Begin by preparing your dough: In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, and salt until well combined.
Next, incorporate the cold, cubed butter into the dry mixture. Use a pastry cutter or your fingers to blend the butter until the mixture looks like coarse crumbs, with some pea-sized pieces remaining.
Gradually add the cold water to the mixture, one tablespoon at a time, stirring gently after each addition. Stop adding water when the dough holds together; be careful not to overwork it to ensure a tender crust.
Once ready, divide the dough into two equal disks. Wrap each disk in plastic wrap and refrigerate for at least 30 minutes. This chilling step is crucial as it helps the butter firm up for a flakier pie crust.
Preheat your oven to 375°F (190°C) and prepare two baking sheets by lining them with parchment paper for easy cleanup.
After the dough has chilled, take one disk out and roll it out on a lightly floured surface to a thickness of about 1/8-inch. Use a cookie cutter or a glass to cut out circles that are approximately 3 inches in diameter. You should have enough for at least 8 hand pies.
On one half of each circle, generously place a handful of mini marshmallows, a sprinkle of crushed graham crackers, and a few chocolate chips, ensuring not to overfill.
Gently fold the other half of the dough over the filling to form a semi-circle. Firmly press the edges together to seal, then use a fork to crimp the edges for a decorative pattern.
Arrange the prepared hand pies on the lined baking sheets. To achieve a nice golden finish, brush the tops with the beaten egg.
Bake in your preheated oven for 20-25 minutes, or until the hand pies are golden brown and slightly puffed.
Once baked, allow them to cool on the baking sheets for a few minutes before transferring them to a wire rack to cool slightly.
Notes
For a delightful serving experience, arrange the hand pies warm on a rustic wooden board. Lightly dust with powdered sugar and serve with a small bowl of melted chocolate for dipping, reminiscent of campfire s’mores. Enjoy!