Preheat the oven to 375 degrees Fahrenheit and spray a large muffin pan with non-stick cookie spray.
Mix the graham cracker crumbs, butter, brown sugar, sugar, and salt in a medium bowl.
Divide the mixture between the muffin spaces and press it into the bottom and sides of the tins using your fingers or a spoon.
Bake for 6-8 minutes or until they are lightly browned. As soon as they come out of the oven, gently press a wooden spoon end into the tins to form it back in shape since they will have puffed up a bit.
Place a marshmallow in the center, then bake again for 6-8 more minutes.
Place a piece of chocolate on top of the marshmallows and let them cool for at least 15 minutes before serving.