Preheat the oven to 400°F
Line a baking sheet with parchment paper or foil
Place graham cracker halves on the baking sheet
Add a piece of chocolate to each graham cracker half
Top each with a marshmallow
Bake for 3 to 5 minutes, until the marshmallows are puffed and lightly golden
Remove from the oven carefully
Top with the remaining graham cracker halves
Press gently and serve immediately