In a shallow dish, use a fork to toss the graham cracker crumbs, sugar, and cinnamon together; set aside.

In a shallow dish, whisk together the egg yolks, whole egg, milk, vanilla, and salt until combined.

Using your hands, soak the bread in the custard until saturated but not falling apart, about 10 seconds per side. Pick up the bread slice and allow excess mixture to drip off. Transfer onto another baking sheet; repeat with the remaining slices.

Place soaked bread slice into the graham cracker coating. Use fingers to gently press coating onto the bread, flip over, and repeat with the other side. Place coated bread slice back onto baking sheet; repeat with the other slices.

Preheat the broiler. Place a wire rack onto a rimmed baking sheet.

In a skillet, heat 1 Tablespoon of butter/oil over medium heat. Once hot enough, transfer two slices to the skillet and cook until golden brown, 2 to 3 minutes per side. Transfer to the baking sheet with the wire rack, and immediately arrange Hershey chocolate sections on top. Wipe the skillet with a paper towel, and repeat steps with the remaining slices, adding 1 Tablespoon more butter/oil for each batch.

Once all slices have been cooked, cut the marshmallows in half* and place about 6-7 marshmallow halves on top of the chocolate. Place under the broiler for 45-60 seconds, or until golden brown, watching CLOSELY so that marshmallows don't burn.

Stack two slices on a plate, and drizzle with melted chocolate and marshmallow fluff.

*To avoid a sticky mess when cutting the marshmallows, I like to grease kitchen shears with cooking spray, then snip the marshmallows in half.