Preheat oven to 350°F. line a 9x13 pan with parchment paper and set rise.
Cream together the butter, granulated sugar and brown sugar.
Add the egg and vanilla. Mix until light in color and creamy.
Add in the dry ingredients (flour, crushed graham crackers, baking soda, baking powder and salt), mix into the dough. Mix until completely combined.
Press 2/3 of the cookie dough into the bottom of the prepared pan.
Top with the Hershey’s chocolate bars.
Spread the marshmallow cream on top of the chocolate bars.
Break the remaining cookie dough into small portions and press onto the marshmallow cream.
Bake at 350° for 30-40 minutes. The cookie dough in the center should no longer look wet and should be turning golden brown. The marshmallow showing through should also be golden brown.
Allow the cookie bars to cool completely and then chill in the freezer for 20 minutes before removing from pan and cutting.
Store at room temp for up to 4 days in an air tight container.