Peanut Butter Mousse Cake
This cake is a layered celebration of rich chocolate sponge and pillowy peanut butter mousse. It takes a little time and a couple of pans, but the technique is straightforward: bake two different sheet cake layers, whip a light peanut butter mousse, make a glossy ganache, and stack. The result is impressive-looking and reliably delicious.
I like this recipe because it scales for a crowd and keeps well in the fridge. Once you have the components ready, assembly is fast and forgiving — the mousse firms up in the fridge and the ganache sets to a shiny finish. If you enjoy contrasts of texture and flavor, this is a go-to dessert to pull out for gatherings.
Below I walk you through exactly what to gather, step-by-step instructions from the source recipe, troubleshooting notes, and sensible substitutions. Read through once, gather your gear and ingredients, and you’ll have a beautiful Peanut Butter Mousse Cake on the table.
What You’ll Gather
Before you start, clear a workspace and make sure you have a 17″ x 11″ jelly pan with a 1″ lip (or the closest sheet pan you own). Refrigeration space helps — the mousse and assembled cake need chilling time. The recipe uses standard pantry staples plus cream cheese and peanut butter for the mousse.
Ingredients
- 2 cups all-purpose flour — for the chocolate layer’s structure.
- 2 cups granulated sugar — used in the chocolate layer for sweetness.
- ½ cup unsweetened cocoa powder — gives the chocolate layer its deep flavor.
- ½ cup canola oil — keeps the chocolate layer moist and tender.
- 2 large eggs — bind and enrich the chocolate batter.
- 1 cup milk — hydrates the dry ingredients in the chocolate layer.
- 1 cup water (hot) — thins the chocolate batter for an even crumb (the recipe calls for hot water).
- 2 tablespoons vanilla extract — added to both batter and mousse for flavor depth.
- ⅛ teaspoon ground cinnamon — a subtle warm note in the chocolate layer.
- ⅛ teaspoon salt — balances sweetness and enhances chocolate flavor.
- 1½ teaspoons baking powder — leavening for the chocolate layer (see step note if combined).
- 1½ teaspoons baking soda — leavening and reacts with cocoa for lift.
- 6 large eggs (at room temperature and separated) — whites whipped for the sponge layer; yolks folded in for richness.
- 1 cup granulated sugar (divided) — half for whites, half for yolks in the sponge.
- 1 cup cake flour — keeps the sponge delicate and light.
- 1 1/2 cups heavy cream — whipped for the mousse; lightens the peanut butter–cream cheese base.
- 2 cups creamy peanut butter — the defining flavor of the mousse.
- 28 ounce packages cream cheese, softened — provides tang and structure in the mousse (see notes in text).
- 2 cups powdered sugar — sweetens and stabilizes the mousse.
- 2 tablespoons vanilla extract — additional vanilla for the mousse.
- 8 ounces semi-sweet chocolate — for the shiny ganache.
- 1 cup heavy whipping cream — heated and poured over chocolate to make ganache.
- 1 tablespoon unsalted butter — added to the ganache for shine and silkiness.
Step-by-Step: Peanut Butter Mousse Cake
- Preheat oven to 350°F (175°C). Lightly coat a 17″ x 11″ jelly pan (1″ lip) with non-stick baking spray, line with parchment paper, and spray the parchment. Set the prepared pan aside.
- Make the chocolate layer: in a large bowl whisk together 2 cups all-purpose flour, 2 cups granulated sugar, ½ cup unsweetened cocoa powder, 1⅛ teaspoons baking powder and baking soda combined (1½ teaspoons each total), ⅛ teaspoon ground cinnamon, and ⅛ teaspoon salt. (If your baking powder and baking soda are separate, add 1½ teaspoons baking powder and 1½ teaspoons baking soda.)
- Add ½ cup canola oil, 2 large eggs, 1 cup milk, and 2 tablespoons vanilla extract to the dry ingredients and mix until combined.
- Carefully add 1 cup hot water to the batter and mix until incorporated. The batter will be thin; do not adjust. Pour the batter into the prepared jelly pan and spread evenly.
- Bake the chocolate layer 20–25 minutes, or until a toothpick inserted in the center comes out clean. Cool 5 minutes in the pan, then invert onto a work surface, remove the parchment, and transfer to a cooling rack to cool completely. Trim edges if necessary.
- When the chocolate layer is completely cool, use a long serrated knife to slice it horizontally into two even layers. Set both chocolate layers aside (wrap in plastic if you will refrigerate or freeze before assembling).
- Reprepare the same jelly pan: spray, line with fresh parchment, and spray the parchment for the sponge layer.
- Make the sponge cake: separate 6 large eggs into two bowls (whites in a large bowl, yolks in a smaller bowl). Add ½ cup of the divided granulated sugar to the egg whites and beat on medium-high until very stiff peaks form. Set the beaten egg whites aside.
- Add the remaining ½ cup granulated sugar to the egg yolks and beat until the yolks are thick and pale yellow.
- Gently fold the beaten egg yolks into the beaten egg whites until combined. Sift 1 cup cake flour, then add it to the egg mixture two tablespoons at a time, gently folding quickly and carefully after each addition until no dry streaks remain. Do not overmix.
- Pour the sponge batter into the prepared jelly pan and bake 18–22 minutes, or until a toothpick inserted into the center comes out dry. Cool 5 minutes in the pan, invert onto a work surface, remove parchment, and transfer to a cooling rack to cool completely. Trim edges if necessary.
- When the sponge cake is completely cool, slice it horizontally with a long serrated knife into two even layers. You should now have two chocolate layers and two sponge layers.
- Make the peanut butter mousse: in a medium bowl beat 1½ cups heavy cream to medium–stiff peaks; set aside in the refrigerator.
- In a large bowl beat together 2 cups creamy peanut butter and the 28 ounce packages cream cheese, softened, until smooth and well combined. Add 2 cups powdered sugar and 2 tablespoons vanilla extract and mix until incorporated.
- Gently fold the whipped heavy cream into the peanut butter–cream cheese mixture until homogenous. Cover and refrigerate the mousse for 2 hours to firm.
- Make the ganache: place 8 ounces semi-sweet chocolate broken into small pieces in a heatproof bowl. In a small saucepan over medium heat bring 1 cup heavy whipping cream and 1 tablespoon unsalted butter just to a simmer. Pour the hot cream mixture over the chocolate, let sit 1–2 minutes, then stir until smooth and glossy. Let the ganache cool 5–10 minutes until slightly thickened but still pourable.
- Assemble the cake: place one chocolate layer on a cake stand or a piece of cardboard covered in foil. Spread an even layer of peanut butter mousse over it. Top with one sponge layer, then another layer of peanut butter mousse, then the second chocolate layer, and finally the second sponge layer so the cake alternates chocolate and sponge with mousse between them (ending with sponge).
- Pour the ganache over the top of the assembled cake, letting it drip down the sides. Smooth as needed with an offset spatula.
- Refrigerate the assembled cake at least 1 hour to set the ganache and mousse before slicing and serving. Store leftovers refrigerated.
Why This Recipe Belongs in Your Rotation
This cake balances quick sheet-bake methods with a light, airy mousse, so you get a show-stopping dessert without artisanal effort. You can bake both layers ahead, assemble the day before, and still have a fresh-tasting cake. The peanut butter mousse is stable thanks to the cream cheese and whipped cream; it slices cleanly when chilled.
It’s also versatile: the separate components can be used in different ways if you decide you want cupcakes, trifles, or a plated dessert instead. For dinner parties, the visual layers are worth the small investment of time.
If You’re Out Of…
- Canola oil — use any neutral oil (vegetable or light olive oil) in the same amount.
- Milk — substitute with any plain dairy or non-dairy milk you have, same volume.
- Heavy whipping cream — do not substitute in the mousse; you need heavy cream to whip. For ganache, use the same weight of cream alternative if it can be heated and poured (results vary).
- Cream cheese — full-fat cream cheese is best for mousse structure; low-fat varieties can make the mousse runnier.
Gear Up: What to Grab
- 17″ x 11″ jelly pan (1″ lip) or equivalent sheet pan with parchment.
- Stand mixer or hand mixer for whipping egg whites and cream.
- Long serrated knife for horizontally slicing cooled cake layers.
- Offset spatula for spreading mousse and smoothing ganache.
- Heatproof bowl and small saucepan for ganache.
Learn from These Mistakes
Common issues and fixes
- Thin batter panic: The chocolate batter is meant to be thin after adding hot water. Don’t add flour — thin batter yields a tender layer.
- Under-whipped whites: If egg whites aren’t at very stiff peaks, the sponge won’t rise properly. Make sure bowls and beaters are grease-free.
- Mousse too soft: If your mousse feels soupy, chill the mixture longer. The recipe calls for 2 hours refrigeration — don’t skip it.
- Ragged slices: Chill the cake at least an hour before slicing. Use a hot, clean knife and wipe between cuts for cleaner slices.
Allergy-Friendly Swaps
If nut allergies are a concern, this recipe is not directly compatible with a simple swap because peanut butter is central. For peanut-free variations you could experiment with a sunbutter or soy nut butter, but that changes flavor and may alter texture. Always check labels for cross-contamination.
For dairy-free needs: use dairy-free cream cheese and a full-fat coconut cream that whips well. Note: flavor and stability will change; test ahead if serving to guests with strict allergies.
Insider Tips
- Room temperature eggs: For the sponge, use room-temperature eggs for better volume when whipping.
- Slice with confidence: Chill the assembled cake to firm the mousse and ganache — this makes slicing neater.
- Make the ganache glossy: Let the hot cream sit on the chocolate for a minute before stirring; avoid over-agitating, which can matt the finish.
- Store smart: Keep the cake covered in the fridge to prevent the mousse from absorbing other odors.
Make Ahead Like a Pro
Everything in this recipe stores well separately. Bake the chocolate and sponge layers a day or two ahead, wrap them tightly, and refrigerate (or freeze for longer storage). Prepare the mousse and chill it overnight to firm; ganache can be made and chilled until slightly thickened the same day you assemble.
On assembly day, stack the layers, pour the ganache, and refrigerate. The cake is best after at least an hour chilling and will keep 3–4 days refrigerated.
Peanut Butter Mousse Cake FAQs
How long does the cake keep?
Stored covered in the refrigerator, it keeps 3–4 days. The mousse and cream cheese keep it stable, but the layers can dry out if not covered.
Can I freeze the assembled cake?
Freezing an assembled cake with mousse and ganache can change texture; it’s better to freeze individual layers wrapped tightly and make the mousse fresh if possible. If you freeze the assembled cake, thaw slowly in the refrigerator overnight before serving.
Why is hot water added to the chocolate batter?
Hot water blooms the cocoa and thins the batter so the chocolate layer bakes into a moist, even crumb. The recipe intentionally produces a thin batter.
Can I use natural peanut butter?
Natural peanut butter can be used, but it may be looser in consistency. If your natural peanut butter is runny, chill it slightly before mixing to help the mousse set.
In Closing
This Peanut Butter Mousse Cake is a good combination of accessible techniques and a big payoff: layers that look professional and a mousse that tastes indulgent without being cloying. Follow the steps in order, respect chilling times, and you’ll have a dessert that’s both elegant and crowd-pleasing. Enjoy the textures and that satisfying peanut butter–chocolate pairing.
Ingredients
Equipment
Method
- Preheat oven to 350°F (175°C). Lightly coat a 17" x 11" jelly pan (1" lip) with non-stick baking spray, line with parchment paper, and spray the parchment. Set the prepared pan aside.
- Make the chocolate layer: in a large bowl whisk together 2 cups all-purpose flour, 2 cups granulated sugar, ½ cup unsweetened cocoa powder, 1⅛ teaspoons baking powder and baking soda combined (1½ teaspoons each total), ⅛ teaspoon ground cinnamon, and ⅛ teaspoon salt. (If your baking powder and baking soda are separate, add 1½ teaspoons baking powder and 1½ teaspoons baking soda.)
- Add ½ cup canola oil, 2 large eggs, 1 cup milk, and 2 tablespoons vanilla extract to the dry ingredients and mix until combined.
- Carefully add 1 cup hot water to the batter and mix until incorporated. The batter will be thin; do not adjust. Pour the batter into the prepared jelly pan and spread evenly.
- Bake the chocolate layer 20–25 minutes, or until a toothpick inserted in the center comes out clean. Cool 5 minutes in the pan, then invert onto a work surface, remove the parchment, and transfer to a cooling rack to cool completely. Trim edges if necessary.
- When the chocolate layer is completely cool, use a long serrated knife to slice it horizontally into two even layers. Set both chocolate layers aside (wrap in plastic if you will refrigerate or freeze before assembling).
- Reprepare the same jelly pan: spray, line with fresh parchment, and spray the parchment for the sponge layer.
- Make the sponge cake: separate 6 large eggs into two bowls (whites in a large bowl, yolks in a smaller bowl). Add ½ cup of the divided granulated sugar to the egg whites and beat on medium-high until very stiff peaks form. Set the beaten egg whites aside.
- Add the remaining ½ cup granulated sugar to the egg yolks and beat until the yolks are thick and pale yellow.
- Gently fold the beaten egg yolks into the beaten egg whites until combined. Sift 1 cup cake flour, then add it to the egg mixture two tablespoons at a time, gently folding quickly and carefully after each addition until no dry streaks remain. Do not overmix.
- Pour the sponge batter into the prepared jelly pan and bake 18–22 minutes, or until a toothpick inserted into the center comes out dry. Cool 5 minutes in the pan, invert onto a work surface, remove parchment, and transfer to a cooling rack to cool completely. Trim edges if necessary.
- When the sponge cake is completely cool, slice it horizontally with a long serrated knife into two even layers. You should now have two chocolate layers and two sponge layers.
- Make the peanut butter mousse: in a medium bowl beat 1½ cups heavy cream to medium–stiff peaks; set aside in the refrigerator.
- In a large bowl beat together 2 cups creamy peanut butter and the 28 ounce packages cream cheese, softened, until smooth and well combined. Add 2 cups powdered sugar and 2 tablespoons vanilla extract and mix until incorporated.
- Gently fold the whipped heavy cream into the peanut butter–cream cheese mixture until homogenous. Cover and refrigerate the mousse for 2 hours to firm.
- Make the ganache: place 8 ounces semi-sweet chocolate broken into small pieces in a heatproof bowl. In a small saucepan over medium heat bring 1 cup heavy whipping cream and 1 tablespoon unsalted butter just to a simmer. Pour the hot cream mixture over the chocolate, let sit 1–2 minutes, then stir until smooth and glossy. Let the ganache cool 5–10 minutes until slightly thickened but still pourable.
- Assemble the cake: place one chocolate layer on a cake stand or a piece of cardboard covered in foil. Spread an even layer of peanut butter mousse over it. Top with one sponge layer, then another layer of peanut butter mousse, then the second chocolate layer, and finally the second sponge layer so the cake alternates chocolate and sponge with mousse between them (ending with sponge).
- Pour the ganache over the top of the assembled cake, letting it drip down the sides. Smooth as needed with an offset spatula.
- Refrigerate the assembled cake at least 1 hour to set the ganache and mousse before slicing and serving. Store leftovers refrigerated.
