Preheat oven to 350° F and grease an 8x8 inch baking dish.
In a large bowl, beat butter and sugar together until light. Add egg and vanilla.
In a small bowl, whisk together flour, graham cracker crumbs, baking soda, and salt. Add to butter mixture, and mix until combined.
Separate the dough in half and press half of it into the bottom of the prepared baking dish. Layer next with the chocolate bars in a single layer, trying not to break the bars unless you have to. Spread the marshmallow cream on top of the chocolate.
With the remaining dough, flatten it into small shingles and piece together so it can cover the chocolate and marshmallows. Press dough gently down.
Bake for 30-35 minutes or until lightly browned. Let cool, then dig in and... ENJOY!
