Makes 4 dozen cookies
Total time: 25 minutes + baking
1 cup all-purpose flour
3/4 cup fine graham cracker crumbs
1/2 tsp. each baking soda and kosher salt
1 stick unsalted butter, softened (8 Tbsp.)
1/2 cup creamy peanut butter
1/2 cup each granulated sugar and packed brown sugar
1 tsp. vanilla extract
24 large marshmallows, halved horizontally
48 Hershey's chocolate bar pieces (4 bars)
Preheat oven to 375 degrees
Whisk together flour, graham cracker crumbs, baking soda, and salt in a bowl.
Cream butter, peanut butter, granulated sugar, and brown sugar in a large bowl with a mixer on medium speed until light and fluffy, 5 minutes. Beat in egg and vanilla until incorporated. Blend in flour mixture on low speed just until incorporated.
Scoop dough with #60 scoop (about 1 Tbsp.) onto ungreased baking sheets.
Bake cookies 4 minutes. Top each with a marshmallow half and bake until golden, 4-5 minutes more. Transfer cookies to cooling racks, press chocolate pieces on top, and let stand 5 minutes.