½ cup crushed graham crackers, plus 4 small crackers
1 cup mini marshmallows, divided
1 teaspoon vanilla extract
1 large egg
⅔ cup milk, more as needed
Directions
In a medium bowl, whisk together the flour, sugar, and salt.
With your fingertips, quickly and gently incorporate the butter into the flour mixture, breaking up any large chunks. Be careful not to overheat the butter.
Add ⅓ cup chocolate chips, ½ cup mini marshmallows, and crushed graham crackers, gently incorporating until well combined.
Mix in the vanilla, egg, and half of the milk. Add more milk only as needed.
Combine ingredients with a fork until a shaggy dough forms.
Dump onto a lightly floured surface, patting into a square, using more flour as needed if the dough is sticky.
Halve the square evenly with a knife or bench scraper and stack one half on top of the other.
Use a rolling pin or pat the dough back into a 6x6-inch square, roughly 1-inch thick.
Divide evenly into four squares.
Press the four graham crackers into the top of each square. Gently press in remaining marshmallows and chocolate chips.
Add squares to a parchment paper-lined baking sheet and chill for 30 minutes (up to overnight) in the refrigerator or freezer.
Preheat the oven to 400 F.
Bake for 15-20 minutes until tops are golden and marshmallows are toasted.