Preheat oven to 375°F and line a 9x13 inch pan with parchment paper.
Beat butter and both sugars until fluffy, then add eggs and vanilla and mix well.
Stir in flour, baking soda, and salt, then fold in crushed graham crackers.
Press two-thirds of the dough evenly into the bottom of the prepared pan.
Layer chocolate bars over the dough, covering as much surface as possible, then scatter marshmallows on top.
Crumble remaining dough in small chunks over the marshmallows and bake for 20 to 25 minutes until golden.
Cool completely before cutting so bars hold their shape.