Preheat oven to 425 degrees F. Line a rimmed baking sheet with a silicone baking mat or parchment paper.
Roll out each pie crust and cut 12 3 -inch circles, re-rolling dough as necessary. Place 6 of the circles on the prepared baking sheet.
Spread 2 tablespoons of marshmallow fluff on each circle, leaving a small border. Top with 3 pieces of Hershey bar, then sprinkle 2 tablespoons graham cracker crumbs. Top with remaining pastry circles.
Crimp edge with a fork. Brush tops of pastries with egg.
Bake in preheated oven for 15 minutes or until pastry is golden brown.
Remove from oven and allow to cool 5 minutes.
Make the glaze: Combine confectioners' sugar, cocoa and milk in a small blow. Spoon glaze over tops of pastries and sprinkle nonpareil sprinkles over top.