In a medium bowl, combine graham cracker crumbles with ¼ cup granulated sugar and then add melted butter and mix to thoroughly saturate the graham cracker crumble.

Firmly press the crust mixture evenly into the bottom of a 9-inch springform pan that has been lined in parchment paper and then set it in the refrigerator while mixing the cheesecake filling.

In a large bowl, with a mixer, mix powdered sugar and vanilla extract into the cream cheese until well combined and smooth.

Mix cool whip with the cream cheese mixture until smooth and creamy.

Divide the mixture evenly into 2 bowls. In one bowl mix in cocoa powder and the remaining ¼ cup of granulated sugar until smooth. In the other bowl mix in the marshmallow fluff.

Remove the springform pan from the refrigerator and spread the chocolate cheesecake filling into the bottom of the pan evenly.

Using a spoon or piping bag, swirl the Nutella over the chocolate cheesecake layer and place the cheesecake in the refrigerator for about 10 minutes or until the Nutella is firm.

Remove the cheesecake from the refrigerator and spread the marshmallow cheesecake over the Nutella and chocolate layer evenly and then refrigerate the cheesecake for at least 1 hour.

For the chocolate topping, in a medium microwave-safe bowl, microwave heavy cream for 1-minute increments until hot but not bubbling, mix in chocolate chips until well dissolved and smooth. It should be very liquid but thick enough to create a layer of chocolate coating. You can add more or less heavy cream to achieve this texture as desired.

Remove the cheesecake from the springform pan. Place the cheesecake on a wire cooling rack over a baking sheet and then pour the chocolate mixture over the cheesecake making sure to coat the entire top and sides. Place back into the refrigerator for a few minutes so the chocolate can firm up.

Top with marshmallows, graham crackers, and chocolate bars then slice the cheesecake and serve cool.