Preheat oven to 325°F (163°C)
Make the crust: Crush 32 regular-stuffed Oreo cookies in a food processor, reserving 20 whole cookies. Mix with melted butter until evenly wet. Press the mixture firmly into a 9-inch springform pan.
Prepare the filling: Beat softened cream cheese with granulated sugar until smooth. Add eggs one at a time, beating well after each addition. Stir in sour cream and 1 ½ tablespoons vanilla extract. Fold in quartered Oreo cookies, then evenly distribute the filling over the crust.
Bake for 1 hour 10 minutes, or until the edges are firm but the center still jiggles slightly. Cool at room temperature before refrigerating for at least 4 hours.
Make the ganache: Melt semisweet chocolate chips with ½ cup heavy cream in a microwave-safe bowl or using a double boiler until smooth. Let cool slightly, then spread over the chilled cheesecake.
Optional whipped cream: Whisk cold heavy cream with powdered sugar and vanilla extract until stiff peaks form. Use as a garnish if desired.