Line a 9×13-inch baking dish with parchment paper, leaving an overhang along the long sides.

Reserve five graham cracker sheets for the topping. Set the remaining crackers aside for the cake layers.

Pour the cooled coffee into a shallow bowl. Stir the espresso powder and hot water together in a separate small dish until dissolved.

Place the Nutella in a medium heat-safe bowl. Heat ½ cup of heavy cream for 45 to 60 seconds, until steaming but not boiling. Pour it over the Nutella, let it stand for two minutes, and whisk until smooth. Cool for 15 minutes.

Beat the softened cream cheese, powdered sugar, vanilla, salt, and dissolved espresso mixture until smooth.

In a separate bowl, beat the remaining two cups of cold heavy cream until stiff peaks form. Fold the whipped cream into the cream cheese mixture in three additions.

Spread ½ cup of coffee cream across the bottom of the dish. Add one layer of graham crackers and lightly brush them with coffee.

Spread half of the remaining coffee cream over the crackers. Add a second graham cracker layer, brush it with coffee, and spread the cooled Nutella mixture over the top.

Add the final cracker layer and brush it lightly with coffee. Spread the remaining coffee cream over the top.

Cover and refrigerate for at least eight hours or overnight.

Crush the reserved graham crackers. Sprinkle the crumbs and optional chopped hazelnuts over the cake shortly before serving.

Cut into 12 squares using a hot, dry knife, wiping the blade clean between cuts.