Preheat oven to 350°F (175°C).

Make the crust: in a medium bowl, stir together 24 Oreo cookies, finely crushed, and 4 tablespoons melted butter until evenly moistened. Press the mixture firmly into the bottom of a 9-inch springform pan. Place the springform pan on a baking sheet and bake for 8 minutes. Remove from oven and set aside to cool while you prepare the filling.

Melt chocolate for the filling: place the (12-ounce) bag semi-sweet chocolate chips in a microwave-safe bowl and microwave on HIGH in 20-second intervals, stirring between each interval, until smooth. Set aside to cool slightly.

Make the cheesecake batter: using an electric mixer, beat 3 (8-ounce) packages cream cheese, softened, at medium speed until smooth and free of lumps. Add the (14-ounce) can sweetened condensed milk and 1 1/2 teaspoons vanilla extract and beat on low until combined. Add 4 large eggs one at a time, beating just until combined after each egg. Beat in the melted semi-sweet chocolate just until evenly incorporated.

Arrange the 12 Reese’s Peanut Butter Cups on top of the cooled Oreo crust in a single layer. Pour the cheesecake batter over the peanut butter cups and smooth the top.

Reduce oven temperature to 300°F (150°C). Place the pan (on the baking sheet) in the oven and bake for 1 hour 5 minutes. After baking, turn the oven off and leave the cheesecake in the oven with the door closed for 1 hour.

Remove the cheesecake from the oven, run a knife around the edge to loosen, and let the cheesecake cool to room temperature. Then remove the sides of the springform pan.

Make the ganache: heat 3/4 cup whipping cream in a small saucepan until it just reaches a simmer. Remove from heat and stir in the (12-ounce) package semi-sweet chocolate chips until smooth. Allow the ganache to cool slightly so it is pourable but not hot.

Pour the ganache over the top of the cheesecake, spreading it to the edges as desired. Refrigerate the cheesecake at least 8 hours (or until fully chilled and the ganache is set).

Make the peanut butter frosting: beat 4 ounces cream cheese, softened, until smooth. Add 1 cup creamy peanut butter and beat until evenly combined. Beat in 2 cups powdered sugar and 2 to 3 tablespoons milk, adding milk as needed until the frosting is thin enough to pipe.

Transfer the frosting to a pastry bag fitted with a large star tip and pipe swirls around the edges of the chilled cheesecake.

Pile the 1 bag mini Reese’s Peanut Butter Cups in the middle of the cheesecake. Keep refrigerated until ready to serve.