In a food processor, crush the Oreos till they become a fine crumb. Add melted butter, stirring until fully combined.
Press into the bottom of the prepared pan, use a cup to tightly press the crumbs into place. Chill in the fridge while you prepare the filling.
Melt the chocolate and heavy cream together, until chocolate is all melted- whisk together- set aside to cool.
Beat cream cheese for 2 minutes on medium to high speed. Add granulated sugar and beat for another minute.
Beat Cream Cheese
Sift in cocoa powder and add in melted chocolate, sour cream, heavy cream, & vanilla mixing until combined- make sure to scrape the bottom of the bowl.
Sift in Cocoa Powder
Add in eggs and yolk one at a time, and mix until just combined. You should have a creamy batter with no lumps.
Pour on top of the crust and use a spatula to spread into an even layer. Place in a water bath and bake.
Turn oven off & let cool in oven for 45 minutes then let cool on the counter for one hour then wrap with plastic wrap and chill for a minimum of 6 hours or overnight.