Preheat oven at 375°F. Set aside a 24-cup mini muffin tin.
Place the graham crackers into a resealable plastic bag and seal tight. Pound with a rolling pin or mallet to pulverize into crumbs.
In a medium bowl, mix together the flour, salt, baking soda and crushed graham crackers, set aside.
In another bowl, mix butter, both sugars, egg and vanilla until combined. Add dry ingredients and mix until it forms a dough.
Scoop about a tablespoon of dough into each prepared mini muffin tin. Use your thumb or a melon baller to make a 1-inch wide impression in the middle of each cup.
Bake 5-7 minutes or until golden around the edges. Remove from oven and then turn on broiler.
Use the spoon to re-indent the centers. Add in 3 mini marshmallows and broil 30-60 seconds to brown.
Remove from oven and add a piece of chocolate to each cup. Broil another 30 seconds to melt. Cool slightly before serving.