Preheat your oven to 325°F (163°C). Prepare a water bath by placing a roasting pan filled with hot water on the bottom rack of the oven.

In a mixing bowl, combine the chocolate cookie crumbs with melted unsalted butter until well mixed. Firmly press this mixture into the bottom of a springform pan.

In a large mixing bowl, beat the room temperature cream cheese and granulated sugar together until smooth. Add in the eggs one at a time, mixing well after each addition, then sprinkle in the hot cocoa mix.

Pour the cheesecake batter over your prepared crust in the springform pan and bake for 50 to 60 minutes, until the edges are set and the center has a gentle jiggle.

Once baking time is up, turn off the oven and let the cheesecake cool in there for about 1 hour. Then transfer to the refrigerator and chill for at least 4 hours.

While the cheesecake cools, pour heavy cream into a mixing bowl and whip until soft peaks form. Gently fold in the marshmallow fluff.

Once the cheesecake has chilled and set, spread the marshmallow whipped cream evenly over the top. Garnish with mini marshmallows and chocolate shavings if desired.