Place oven rack in upper third of oven and preheat broiler. Line a baking sheet with aluminum foil.

Place graham crackers in a large, zip-top bag and crush, using a mallet or the bottom of a pan.

Using a serrated knife, slice the cake horizontally into 3 equal layers. Place the bottom layer on the prepared baking sheet. Spread on half of the Nutella, and sprinkle on 2-3 tablespoons of graham cracker crumbs. Top with the middle layer of pound cake, spread on remaining Nutella and sprinkle on another 2-3 tablespoons graham cracker crumbs. Top with last layer of cake.

Using an offset spatula or knife, spread the marshmallow fluff all over the top and sides of the cake, completely covering it.

Place the cake underneath the broiler and cook, keeping a close eye on it, until the marshmallow fluff is browned to your liking. Remove from oven and let it cool so that the marshmallow coating hardens a bit.

To serve, cut cake into slices with a serrated knife. Place each slice on a plate and sprinkle more graham cracker crumbs around the edges.