Preheat oven to 350°F and line an 8x8 pan with parchment paper. Place graham crackers in an even layer across the bottom of the pan.
In a bowl, mix together all ingredients, except for the marshmallows, until you have a dough.
Press the dough evenly on top of the graham crackers and bake for about 10 min.
Remove from oven and top with the marshmallows. Add optional crushed graham crackers on top too. Return to oven for about 3 minutes until the marshmallows start to grow in size.
Broil for about 1 minute to brown the tops of the marshmallows. Let cool before slicing and enjoying!