Preheat oven to 325°F (160°C) and grease a 9-inch springform pan.
Crush Oreo cookies in a food processor, add melted butter, and mix until fully combined and sticky.
Press the mixture evenly into the bottom of the prepared pan to form the crust.
Chop bittersweet and semi-sweet chocolate into small pieces and melt over a double boiler or in the microwave at 50% power, stirring frequently.
In a separate bowl, whisk together heavy cream, sugar, and vanilla extract until soft peaks form.
In another large bowl, beat cream cheese until smooth, then gradually add cooled melted chocolate and mix until fully combined.
Fold in the whipped cream gently to avoid deflating it.
Pour the chocolate filling mixture over the Oreo crust and smooth it out with a spatula.
Cover the springform pan with aluminum foil and place it in a roasting pan filled with hot water (bain-marie method) to bake evenly.
Bake for 65–70 minutes or until the edges are set and the center still jiggles slightly.
Remove from the oven and let cool to room temperature, then refrigerate for at least 4 hours or overnight.
Before serving, top with optional chocolate shavings, whipped cream, or cocoa dust for a finishing touch.