Preheat oven to 300° F. Line two muffin tins with cupcake liners (24 total) and set aside.
Oreo Crust
Place the oreos in a ziploc bag and crush with a rolling pin until they are turned into a fine dust. In a bowl, mix together with the melted butter.
Evenly distribute the oreo crust between the 24 cupcake liners, and then gently press into a flat layer.
Cheesecake Filling
Using a standing mixer or handheld mixer, mix the cream cheese, cocoa powder, and sugar on high for 2-3 minutes. Add the sour cream, heavy cream, and vanilla extract. Mix on medium speed until well-combined and creamy. Add the eggs and egg yolks, then mix on medium-low until well combined. If using a standing mixer, scrape down the sides of the bowl occasionally to make sure everything is mixed well.
Melt the chocolate in the microwave for 30 seconds at a time. After each 30 seconds, stir. This should only take about a minute total in the microwave.
Once the chocolate is completely melted, wait a minute or two for it to cool off and then add it to the filling. Mix on medium speed, occasionally scraping down the sides of the bowl to make sure it is all evenly combined.
Evenly distribute the filling between the muffin tins, on top of the oreo crust.
Bake each tin separately for 15-18 minutes each, until the cheesecake centers are mostly set but still slightly jiggly in the center. Remove from the oven and allow to cool for 30 minutes.
Chocolate Ganache
Heat a small sauce pan on the stove's lowest setting. Add the chocolate chips, cream, and cubed butter. Continually stir for about 5-10 minutes, until all the ingredients melt and the ganache is smooth and shiny. Don't rush this step, or it will burn.
Add a spoonful of ganache on top of each cheesecake, and smooth over with a knife.
Loosely cover the cheesecakes with plastic wrap and refrigerate overnight, or at least 8 hours.
Whipped Cream
Add the heavy whipping cream, powdered sugar, and vanilla extract to a standing mixer and mix on high until soft peaks form. If you'd like a stiffer whipped cream, add extra powdered sugar.
Pipe the whipped cream on top of each cheesecake, adding a mini Oreo on top. Refrigerate until ready to serve. Enjoy!
Notes
*You can use normal unsweetened cocoa powder, or Dutch-process cocoa powder(my personal favorite). Dutch-process cocoa powder will have a deeper, richer flavor.