CRUST: Begin by making the crust. Preheat the oven to 325° F. Crush up the Oreo cookies using a food processor or place in a ziplock bag and crush with a rolling pin. Add melted butter and mix until combined. Press the crust into a 9" springform pan, working the crumbs about half way up the side. (Pressing the crust in using a measuring cup is really handy!) Bake for 10 minutes. Remove from oven and set aside to cool.
CHEESECAKE: Optional water bath: Wrap your springform pan in heavy duty aluminum foil. You can also double wrap it by layering a plastic crockpot liner bag. We do this to prevent any water from coming into the pan as it cooks in a water bath. Set aside. Pull out a roasting pan or large baking dish - something large enough for the cheesecake pan to sit in. (This water bath is optional, but helps prevent the cheesecake from cracking. If it does crack, no worries - it'll be covered with a ganache!)
Gather the cold ingredients and bring to room temperature. Melt chocolate (in slow increments to avoid seizing) and set aside to begin letting it cool.
Using a stand mixer or large bowl and hand mixer, mix together the softened cream cheese , flour, sugar, and cocoa powder until smooth and light, about 1 minute.
Add heavy cream and vanilla. Gently mix. Add the cooled down melted chocolate and mix.
Add eggs one at a time, gently mixing after each one. After you add the eggs, avoid over mixing at this point.
Pour batter into prepared crust. Bake for about 75 minutes until the edges of the cheesecake are set and the center is just slightly jiggly. Add more time if needed. Turn off the oven and crack the oven door to allow the cheesecake to cool slowly for one hour. (This slow cool process also helps prevent cracking!)
GANCHE: In a microwave safe bowl, heat up butter and whipped cream till almost boiling. Add chocolate chips and cover for 2 minutes.
After 2 minutes, whisk the mixture together till smooth and silky. If you need to heat it in the microwave for a bit longer to help mix, that's fine. Spread on top of the cheesecake. I used an offset spatula to help gently push over the sides to help it cascade down a bit, but you could just leave it on the top!
Place it in the fridge to finish chilling for at least a few hours. Add chocolate shavings if desired. (I just used a vegetable peeler against a chocolate bar to create the shavings!)