Combine 1 ½ cups of crushed Oreo cookies with ¼ cup of melted butter in a mixing bowl. Stir until well-coated. Press into the bottom of a springform pan. Chill for 30 minutes.

Melt 4 oz of dark chocolate. Cool slightly. Whip 1 cup of heavy cream with 1 tablespoon of sugar until soft peaks form. Optional: dissolve 1 teaspoon of gelatin in warm water and stir into chocolate. Fold whipped cream into chocolate and spread over crust. Chill for 30 minutes.

Melt 4 oz of milk chocolate until smooth. Let cool, whip another cup of heavy cream with 1 tablespoon of sugar to soft peaks. Fold whipped cream into milk chocolate, layer on top of dark chocolate mousse, smooth, and chill for 30 minutes.

Melt 4 oz of white chocolate, let cool. Whip last cup of heavy cream with remaining tablespoon of sugar to soft peaks. Fold whipped cream into white chocolate, layer on top of milk chocolate mousse, smooth, and chill for at least 4 hours.

Loosen the cake from the springform pan, transfer to serving platter, and garnish with optional toppings. Slice with a warm knife and serve.