Line a baking sheet with parchment paper. Lay graham cracker squares out evenly across the pan. Top half of the crackers with marshmallows and the remaining half with chocolate pieces.
Place baking sheet in the top half of the oven. Turn on the broiler and watch the marshmallows until they brown to your liking. This takes about 1 to 2 minutes. Do not walk away because marshmallows can burn quickly.
Remove from oven. Turn the marshmallow halves over onto chocolate halves to create sandwiches. Serve warm.
Notes
Can't use your broiler? S'mores can be baked traditionally instead. Preheat oven to 425 degrees Fahrenheit, then bake s'mores for about 5 minutes, or until browned to your liking.
Graham crackers substitutions: Pretzel chips, crackers, or cookies.
Chocolate substitutions: Your favorite chocolate candy, peanut butter, or Nutella.