Step 1: Prepare the Oreo Crust - Preheat your oven to 350°F (175°C). Crush the 20 Oreos into fine crumbs and combine with melted butter. Press into the bottom of a 9-inch springform pan. Bake for 10 minutes and let cool.
Step 2: Melt the Chocolate - Melt the 1 pound of semi-sweet chocolate in a double boiler or microwave. Stir in 1 teaspoon of vanilla and 1/4 teaspoon of salt. Let cool slightly.
Step 3: Whip the Cream - In a large bowl, whip 2 cups of heavy cream with 1 tablespoon of sugar until stiff peaks form. Fold half into the chocolate mixture.
Step 4: Prepare the Egg Mixture - Whisk 2 whole eggs and 4 egg whites until frothy. Fold into the chocolate mixture.
Step 5: Combine with Remaining Whipped Cream - Gently fold in the remaining whipped cream.
Step 6: Chill the Mousse - Pour the mousse over the cooled crust. Smooth the top and refrigerate for at least 4 hours.
Step 7: Make the Peanut Butter Topping - Beat 1 1/2 cups of heavy cream, 1/2 cup of peanut butter, 3 tablespoons of powdered sugar, and 1 teaspoon of vanilla until soft peaks form. Spread over the mousse.
Step 8: Decorate and Serve - Melt 3 oz. of chocolate with 1/2 teaspoon of vegetable oil. Drizzle over the peanut butter layer. Garnish with crushed Oreos and fresh berries.