Instructions

1. Coat a 9-inch round springform pan with cooking spray. Place 4 tablespoons unsalted butter in a small microwave-safe bowl and microwave on high until just melted, 20 to 30 seconds.
2. Place 20 Oreo cookies in a food processor fitted with the blade attachment. Pulse until finely chopped, about 10 (1-second) pulses. Add the butter and pulse until combined, about 8 (1-second) pulses. Transfer to the pan and press evenly into the bottom with your fingertips or the bottom of a measuring cup. Refrigerate while you make the chocolate layers.
3. Place 2 tablespoons of the cold water in a small bowl and sprinkle with 1 1/2 teaspoons of the powdered gelatin. Place the remaining 2 tablespoons cold water in a second small bowl and sprinkle with the remaining 1 1/2 teaspoons powdered gelatin. Let both sit to hydrate for at least 5 minutes.
4. Place 8 ounces dark chocolate chips in a medium or large heatproof bowl. Place 8 ounces milk chocolate chips in a second medium or large heatproof bowl.
5. Bring 1 cup of the heavy cream to a simmer in a small saucepan over medium-high heat. Remove the pan from the heat. Add one of the hydrated gelatin portions and whisk until smooth and the gelatin is dissolved. Pour over the milk chocolate chips and stir until the chocolate is melted and the mixture is smooth and combined. Let cool until room temperature, about 20 minutes.
6. Wash and dry the saucepan. Add 1 cup of the heavy cream into the same saucepan and bring to a simmer over medium-high heat. Remove the pan from the heat. Add the remaining hydrated gelatin and 2 tablespoons dark cocoa powder, and whisk until smooth and the gelatin and cocoa powder are dissolved. Pour mixture over the dark chocolate chips and stir until the chocolate is melted. Let cool until room temperature, about 20 minutes.
7. Place the remaining 2 cups cold heavy cream, 1/2 cup powdered sugar, 2 teaspoons vanilla extract, and 1/4 teaspoon kosher salt in a large bowl if using an electric hand mixer (or stand mixer fitted with the whisk attachment). Beat on medium-high speed until firm peaks form, about 3 to 4 minutes.
8. Divide the whipped cream between the dark and milk chocolate mixtures (about 2 cups per bowl). Fold the whipped cream into the dark chocolate mixture with a flexible spatula just until combined and no streaks remain. Dollop into the crust and smooth into an even layer. Refrigerate until just set, about 20 minutes. Meanwhile, fold the cream into the milk chocolate mixture and let sit at room temperature.
9. Dollop the milk chocolate mixture over the slightly chilled dark chocolate layer and smooth into an even layer. Cover and refrigerate until the cake is fully set, at least 4 1/2 hours and up to 3 days.
10. To serve, run an offset spatula around the edges of the pan to loosen, then remove the sides of the pan. Top with 1 pint fresh raspberries. Slice with a chef’s knife and serve cold. For the cleanest cuts, use a knife run under warm water and wiped dry for each cut.