Preheat the oven to 325°F (160°C).

In a mixing bowl, combine finely crushed Oreo cookies with melted unsalted butter. Press this mixture into the bottom of a 9-inch springform pan.

Bake the crust for 11 minutes and let it cool.

In a large mixing bowl, beat cream cheese and granulated sugar until smooth. Blend in hot cocoa mix, cocoa powder, sour cream, heavy cream, and vanilla extract. Add eggs one at a time.

Place the filled springform pan into a larger roasting pan and pour hot water halfway up the sides of the springform pan.

Bake for 75-85 minutes until the edges are set but the center jiggles.

Turn off the oven and crack open the door, allowing the cheesecake to cool for 30 minutes. Remove from the water bath and let cool completely for at least 6 hours.

In a mixing bowl, beat heavy cream with powdered sugar and vanilla extract until medium peaks form. Spread whipped cream on top of the cooled cheesecake.