1. Preheat oven to 375 degrees. Mix together butter and sugar together until creamy. Add vanilla and egg and mix until well combined.
2. In a medium bowl, stir together graham cracker crumbs, flour, baking soda and salt. Add, a bit at a time, to the butter mixture until combined. Fold in the chocolate chunks.
3. Using a cookie scoop or a tablespoon, drop dough about 2" apart onto parchment lined baking sheets. Flatten dough ball slightly with your hand and place a marshmallow half on top.
4. Bake for 8-10 minutes, or until marshmallow is lightly browned.