Preheat oven to 375 degrees. Spray 12-cup muffin tin with cooking spray and set aside.
In a large bowl, whisk flour, cracker crumbs, sugar, baking soda and salt.
In a separate bowl, whisk the egg, buttermilk, oil and vanilla until combined.
Add buttermilk mixture into flour mixture, stirring gently until just combined. Fold in chocolate chips and 1 cup marshmallows.
Divide batter evenly among prepared muffin cups. Top with remaining marshmallows (2-3 marshmallows per muffin).
Bake for 13 to 15 minutes, or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before gently removing from pan. Move to a wire rack to cool completely.
Recipe by Alida's Kitchen at https://www.alidaskitchen.com/2012/07/03/smore-muffins/