Remove filling from chocolate sandwich cookies if using Oreos, or use pre-crushed chocolate cookie crumbs. Pulse cookies in a food processor until fine and even, resembling wet sand.
Transfer cookie crumbs to a medium bowl. Pour melted butter over crumbs and mix with a fork until evenly moistened and the mixture holds together when pressed.
Press mixture firmly into the bottom and up the sides of a 9-inch pie pan. Use the bottom of a measuring cup or glass to pack tightly. Chill in the refrigerator while preparing the filling.
In a large mixing bowl, beat softened cream cheese with an electric mixer on medium speed for about 2 minutes until smooth and fluffy.
Add peanut butter to the cream cheese and continue beating for another minute until well combined and creamy.
Gradually add powdered sugar, about half a cup at a time, beating well after each addition. Add vanilla extract and mix until incorporated.
In a separate bowl, whip heavy cream with clean beaters on high speed until stiff peaks form, about 3-4 minutes.
Gently fold one-third of the whipped cream into the peanut butter mixture using a rubber spatula in a circular motion. Fold in remaining whipped cream in two additions, being careful not to deflate. Filling should be light, fluffy, and smooth.
Remove chilled crust from refrigerator. Pour peanut butter filling into prepared crust and spread evenly with a rubber spatula or offset spatula, reaching all edges.
Smooth the top as much as possible. Tap the pie pan gently on the counter a few times to release air bubbles. Return to refrigerator and chill for at least 2 hours, or until filling is firm to the touch.
Place chocolate chips in a medium, microwave-safe bowl. Heat heavy cream in the microwave for about 60-90 seconds until steaming and just begins to bubble around the edges. Pour hot cream over chocolate chips.
Let mixture sit undisturbed for 2 minutes. Whisk slowly from the center outward until chocolate is completely melted and ganache is smooth and glossy. Microwave in 10-second intervals if needed. Let cool for about 10 minutes until still pourable but slightly thickened.
Remove chilled pie from refrigerator. Pour ganache over the center of the pie and spread gently to the edges with an offset spatula or the back of a spoon, being careful not to disturb the peanut butter layer. Work quickly before ganache sets.
While ganache is still soft, arrange mini peanut butter cups around the edge or in a decorative pattern on top. Optionally drizzle melted peanut butter over the ganache. Return pie to refrigerator and chill for at least 2 more hours, or until ganache is set.