Preheat oven to 375 degrees. Line a 13x9-inch pan with nonstick foil.
Lay graham crackers in a layer covering the full pan, breaking up some into pieces to cover smaller areas on edges.
Beat butter and sugars. Add eggs and vanilla.
Add the flour, salt, baking soda. Then add chocolate chips and mini marshmallows.
Press cookie dough over the graham crackers. Cover top generously with mini marshmallows.
Bake at 375˚F for approx 30 minutes or until golden brown. (Check at 25 mins.)
Remove from oven and lay chocolate pieces on top while still warm. Cool at least 30 mins before cutting.