In a large bowl, combine flour and salt. Use a pastry blender to cut butter into flour until mixture resembles coarse crumbs. Stir in water, 1 tablespoon at a time, until mixture just begins to form a dough. Divide in half and wrap each with plastic wrap. Refrigerate at least 1 hour.

Preheat oven to 375°F. Line 2 baking sheets with parchment paper and set aside.

Working with half the dough at a time, roll out on a floured work surface to a large rectangle, about 1/4 –inch thick. Using a sharp knife or a pizza cutter, trim the edges to form a smooth rectangle. Cut into 12 smaller rectangles and place 6 rectangles on each baking sheet. Place a tablespoon of peanut butter on each square and sprinkle with chocolate chips and marshmallows. Roll out second dough half, trim the sides and cut into 12 even rectangles. Place 1 rectangle on each filling-topped rectangle and crimp the sides together using a fork. Use a sharp paring knife to make a few slits on top of each hand pie to allow steam to escape during baking.

Brush the hand pies with egg wash and sprinkle with graham cracker crumbs and sugar. Bake until golden brown, about 25 to 30 minutes. Remove from oven and allow to cool before serving. Enjoy!