Whisk your eggs in a bowl with the milk and generously sprinkle the cinnamon; whisk until fluffy
Crush the graham crackers in a food processor until crumbs; spread on a plate
Slice marshmallows in half, so they'll lay flat on the bread.
Preheat your skillet, spray with cooking spray and a small pat of butter.
Lay pieces of bread in the egg mixture on both sides, onto the graham cracker crumbs, then immediately onto the heated skillet.
Fry the bread on both sides, one at a time, until golden brown, crisp, and toasted well.
Place the prepared toast on a plate and spread with Nutella.
Lay sliced marshmallows on next, and top with chocolate squares (and more Nutella, if desired)
Prepare another french toast and place immediately on top, pressing down while hot.
At this point, if you'd like, you can place the stuffed french toast into a panini press or sandwich maker to further cook and press together, if desired.