Preheat the oven to 350F.
In a small mixing bowl, combine the graham cracker crumbs, powdered sugar, and melted butter.
Grease a 24 cup mini muffin tin with non-stick cooking spray.
Scoop the graham cracker crust mixture into the 24 cups.
Gently press the crumbs into the bottom of each cup and up the sides to form little cups.
Bake the mini graham cracker crusts at 350F for 4 minutes until golden brown.
Cut each marshmallow in half to make 24 round marshmallows.
Place one marshmallow in each graham cracker cup, cut side of the marshmallow facing down.
Set the oven to broil. Place the pan back in the oven under the broiler and broil for 1-2 minutes, just until the marshmallows are toasted to your liking.
Watch them CAREFULLY, the marshmallows can burn fast.
Remove from the oven.
Top each marshmallow with a piece of the Hershey's chocolate bar. Allow the s'mores cookie cups to cool for 15 minutes, then use a butter knife to remove them from the pan.
ENJOY!