Line a 9 x 13 baking pan with foil, lightly spray with non-stick cooking spray. Combine crushed Oreo cookies with melted butter until all crumbs are moistened. Press crumb mixture into bottom of prepared pan. Set aside.
Place 1 cup chocolate chips in a microwave safe bowl. Heat on high in microwave for 45 seconds. Remove from microwave and stir until chocolate is completely melted. Heat an additional 15 seconds if needed. Let cool.
Cream cream cheese until smooth. Add in sugar and vanilla, beat well. Add cooled chocolate and beat again until combined. Add in eggs, one at a time, beating just until combined. Make sure to scrap down sides of bowl.
Spoon cheesecake mixture over prepared crust and smooth to edges. Bake in a preheated 325°F oven for 40-45 minutes, until only center of cheesecake jiggles. Turn off oven and leave cheesecake in oven with door to oven cracked for 1 hour.
After 1 hour, remove cheesecake to rack to cool completely before refrigerating. Let cheesecake chill for 1 hour before adding decorative ganache.
To make ganache:
Place chocolate chips and cream in a microwave safe bowl. Heat on high for 1 minute. Let chocolate rest for 5 minutes before stirring. Stir until completely smooth. Let cool.
Spoon ganache into a pastry bag fitted with a #3 tip or you can use a plastic freezer bag with a small hole cut out of one corner. Drizzle chocolate ganache over cheesecake in any design. Refrigerate for at least 4 hours to completely chill before slicing.