Preheat the oven to 350°F. Line a baking sheet with parchment paper and set aside.
Roll out the pie crust on a lightly floured surface. Use a heart-shaped cookie cutter to cut as many as you can fit. Repeat with second dough sheet. Try to get the same number of hearts for each dough sheet.
Place the first sheet of hearts onto the prepared baking sheet. These will be the bottoms of the hand pies.
Add the filling. Spoon about 1-2 teaspoons of jelly or jam into the center of each heart. Be careful not to overfill, as this can cause the filling to leak while baking.
Seal the hand pies. Place the other set of hearts on top of each hand pie with the filling. Use a fork to press around the edges to seal completely.
Prepare the egg wash. In a small bowl, whisk the egg until smooth. Lightly brush the tops of each hand pie with the egg wash.
Bake for 16–18 minutes, or until the hand pies are lightly golden brown and the crust is cooked through.
Remove from the oven and allow the hand pies to cool on the baking sheet or a wire rack before icing.
While the hand pies are cooling, prepare the icing. In a small bowl, stir together the powdered sugar and milk until smooth. Add a little more or less milk, as needed, to reach a thick but still drizzly consistency. Optional: for added flavor cut back a little on the milk and add a tiny splash/drop of vanilla, almond, or lemon extract!
Time to decorate! Smooth icing onto the cooled hand pies and top with sprinkles. Allow icing to set before serving.