Preheat your oven to 325°F (160°C) and set up a water bath with a roasting pan filled with hot water on the bottom rack.

In a mixing bowl, combine chocolate cookie crumbs and melted unsalted butter until it resembles wet sand. Press into the bottom of a springform pan.

In a large bowl, beat room-temperature cream cheese and granulated sugar until smooth. Add eggs one at a time, then mix in the hot cocoa mix until well blended.

Pour the cheesecake filling over the crust and place it in the oven within the water bath. Bake for 50 to 60 minutes.

Once baked, turn off the oven and let the cheesecake cool inside for about 1 hour, then refrigerate for at least 4 hours.

Whip the heavy cream until soft peaks form, then gently fold in the marshmallow fluff until fully combined.

Spread the marshmallow whipped cream over the top before serving, and garnish with mini marshmallows and chocolate shavings if desired.