Line a baking sheet with parchment paper. Lay graham crackers in a single layer to cover the bottom of the pan. Set aside.
Preheat oven to 375°F.
In a small saucepan over medium-high heat, melt butter. Add in sugar and bring to a rolling boil, stirring constantly. Once boiling, pour over graham crackers.
Place in oven on middle rack and cook for 10 minutes. Sprinkle marshmallows evenly over the top and add the chocolate pieces. Return to the oven for an additional 2-4 minutes, until marshmallows begin to brown.
Remove from oven and cool completely. Once cooled, cut into bite sized pieces and enjoy. Store in airtight container.