**For the Oreo Crust:**

1. Preheat the oven to 350°F.
2. Crush the Oreos in a food processor until finely ground.
3. Mix the Oreo crumbs with melted butter and press onto the bottom and sides of a 9-inch springform pan.
4. Bake for 10 minutes, then let it cool.

**For the Chocolate Cheesecake:**

1. Preheat the oven to 350°F.
2. In a mixing bowl, beat cream cheese, sugar, and cornstarch until smooth.
3. Add sour cream, vanilla, and melted chocolate, mixing until well combined.
4. Gradually add eggs and egg yolks, one at a time, mixing well after each addition.
5. Pour the batter into the prepared crust.
6. Place the springform pan in a larger roasting pan, then pour boiling water into the roasting pan to create a water bath.
7. Bake for 1 hour, then let it cool in the oven with the door cracked open.
8. Once cooled, refrigerate for at least 8 hours.

**For the Whipped Chocolate Ganache:**

1. Heat cream until boiling, then pour over chopped chocolate.
2. Let it sit for a minute, then stir until smooth.
3. Let it cool to room temperature, then whip with an electric mixer until light and fluffy.
4. Transfer to a piping bag.

**For the Chocolate Ganache for on Top of the Cheesecake:**

1. Heat cream until boiling, then pour over chopped chocolate.
2. Let it sit for a minute, then stir until smooth.
3. Let it cool for 3-5 minutes until slightly warm but not hot.

**Assembling the Cheesecake:**

1. Top the chilled cheesecake with chocolate ganache and smooth it out.
2. Return to the fridge until set.
3. Pipe swirls of whipped chocolate ganache around the edges.
4. Serve and enjoy! Store leftovers in the fridge for up to five days.