Instructions

• Make the crust: Add 30 Oreo cookies to a food processor and pulse until very fine crumbs. Transfer crumbs to a bowl and stir in 5 Tablespoons (70 g) melted butter until evenly combined. Pour the mixture into a 9-inch springform pan and press firmly into the bottom and about halfway up the sides using the back of a spoon or measuring cup. Refrigerate the crust while you prepare the filling.
• Preheat the oven to 325°F.
• Make the cheesecake filling: In a large bowl, beat 12 ounces (340 g) softened cream cheese with 3/4 cup (150 g) granulated sugar until smooth and free of lumps. Add 2 large eggs and 1 large egg yolk, mixing each just until combined. Add 1 1/2 teaspoons vanilla extract, then fold in 1 cup (230 g) sour cream or plain Greek yogurt until the batter is smooth.
• Assemble and bake: Pour the cheesecake filling evenly over the chilled Oreo crust and smooth the top. Bake at 325°F for 45–60 minutes, or until the edges are set and the center is slightly firm but may still jiggle a little.
• Cool the cheesecake: Remove the cheesecake from the oven and place it on a wire rack to cool to room temperature (about 1–2 hours). Once at room temperature, refrigerate the cake until completely chilled before adding the mousse (chill at least 1–2 hours or overnight if you prefer).
• Prepare the chocolate base for the mousse: Place 1 1/3 cups (226 g) semi-sweet chocolate chips in a heatproof bowl. In a small saucepan or microwave-safe container, heat 1/2 cup (120 g) of the heavy whipping cream until hot but not boiling. Pour the hot cream over the chocolate chips and let sit for 2–3 minutes, then stir until completely smooth. Allow this chocolate mixture to cool to room temperature (do not refrigerate).
• Whip the remaining cream: Pour the remaining 1/2 cup (120 g) heavy whipping cream into a mixing bowl, add 1/2 teaspoon vanilla extract, and whip to stiff peaks using an electric mixer.
• Make the mousse: Gently fold the whipped cream into the cooled melted chocolate mixture in two additions, folding until uniform and light. Spread the mousse evenly over the chilled cheesecake surface.
• Chill the mousse layer: Refrigerate the cheesecake with the mousse layer for at least 3–4 hours, or overnight, until the mousse is set.
• Make the ganache: Place 1/2 cup (85 g) semi-sweet chocolate chips in a small bowl. In a small saucepan, combine 4 Tablespoons (56 g) butter and 1/4 cup (60 g) heavy whipping cream and heat over medium until the mixture just begins to simmer (do not boil). Pour the hot butter-cream mixture over the chocolate chips and stir until smooth and glossy. Stir in 1/2 teaspoon vanilla extract and 1 Tablespoon (7.5 g) powdered sugar until fully incorporated.
• Finish the cheesecake: Pour the ganache over the chilled mousse layer and spread gently to the edges. Return the cheesecake to the refrigerator and chill at least 1 hour to set the ganache before serving.
• Serve: Run a warm knife around the edge of the springform before releasing the ring for clean slices; slice and serve chilled.