Preheat oven to 325°F. Spray a 9-inch springform pan with nonstick spray and line the bottom with a round of parchment paper.

In a large bowl, using an electric mixer on medium speed, beat the first Two 8-ounce packages cream cheese until smooth and creamy and free of lumps.

Add ⅔ cup granulated sugar and ½ teaspoon salt to the cream cheese and beat for about 2 minutes, stopping once or twice to scrape down the sides and bottom of the bowl.

Add the 2 large eggs one at a time, beating briefly after each addition just until incorporated.

Add ⅓ cup sour cream, ⅓ cup heavy whipping cream, and 1 teaspoon vanilla extract. Mix until the batter is smooth and homogenous.

Fold in ½ cup miniature chocolate chips with a spatula or spoon.

Pour the cheesecake batter into the prepared springform pan and smooth the top. Bake at 325°F for about 45 minutes, or until the center is set and the surface is not jiggly.

Remove the cheesecake from the oven and place it on a wire rack. Let it cool at room temperature for at least 1 hour.

After cooling, remove the springform sides, slide a knife under the parchment, and lift the cheesecake out. Peel off the parchment, then place the cheesecake (on a plate or baking sheet) into the freezer and freeze completely (several hours or overnight).

When ready to bake the cake layers, preheat oven to 350°F. Grease and flour two 9-inch round cake pans and line the bottoms with parchment rounds.

In a large bowl, combine One 15.25-ounce box white cake mix, 1¼ cups water, ⅓ cup canola or vegetable oil, and 3 large egg whites. Use a hand mixer on medium speed to mix until smooth.

Stir in 1 cup miniature chocolate chips by hand until evenly distributed.

Divide the batter evenly between the two prepared pans, filling each pan to about 3/4 full or about 1 inch below the rim.

Bake the cake layers at 350°F for 30–35 minutes, or until a toothpick inserted in the centers comes out clean. Begin checking at 30 minutes and then every 5 minutes until done.

Let the cake layers cool in the pans for about 20 minutes, then turn them out onto cooling racks and cool completely.

While cakes cool, make the frosting: In a large bowl, using an electric mixer on medium-high speed, beat the second Two 8-ounce packages cream cheese, ½ cup (1 stick) salted butter (both at room temperature), 2½ cups sifted powdered sugar, and 1 tablespoon vanilla extract until smooth and creamy. Do not overbeat.

Place one cooled cake layer on a cake plate or platter. Spread a thin layer of frosting over the top of that layer (this will help the cheesecake adhere).

Remove the frozen cheesecake from the freezer, remove any remaining parchment, and set it on a cutting board. If the cheesecake is larger than the cake layers, trim the outer edge of the cheesecake to match the cake diameter using a long knife (work quickly while the cheesecake is frozen).

Place the cheesecake layer on top of the frosted bottom cake layer. Spread a thin layer of frosting over the top of the cheesecake.

Place the second cake layer on top of the cheesecake, pressing lightly to level.

Apply a thin, even crumb coat of frosting over the entire stacked cake. Chill the cake in the refrigerator for 15–30 minutes to set the crumb coat.

Finish frosting the cake with the remaining frosting: start with a large scoop on top, spread evenly across the top, then down the sides with a long, thin spatula. Add more frosting as needed to cover bare spots and smooth the surface. Optionally use a piping bag for a decorative edge.

Press extra miniature chocolate chips onto the top and sides of the cake as garnish.

Refrigerate the assembled cake until ready to serve. Store leftovers refrigerated.