Preheat oven to 325 degrees.
Crush Oreo cookies in a food processor. Mix crumbs with melted butter; press into 9-inch spring form pan or mini cheesecake pan. Bake for 10 minutes.
Beat cream cheese, sugar, and vanilla until well combined.
Add eggs, mix just until blended.
Pour over Oreo crust.
Bake 45-55 minutes, or until center is almost set.
Cool before removing from pan.
Refrigerate for 4 hours.
For the ganache:
Heat cream in a small sauce pan until it begins to boil. Remove from heat and pour over chocolate in a large bowl. Whisk until smooth.
Allow ganache to cool slightly before pouring over cheesecake. Top with chopped Reese's cups.