On a lightly floured surface, roll out the pie dough into a large rectangle that is 1/4 inch thick. Cut the dough into 4-inch by 2-inch rectangles. In a small bowl, whisk together the egg and water to make an egg wash.
Place a piece of dough on a flat surface in front of you. Spread 1 tablespoon preserves or cream cheese in the center of the dough and top with 1 heaping tablespoon fresh fruit.
Use your fingertip to spread the edges of the pie dough with the egg wash, and then top with another piece of dough.
Use the tines of a fork to crimp the edges of the pie dough. Gently puncture the top dough with the fork. If you want the pop tarts to look extra golden brown, brush the tops with a little egg wash.
Bake the pop tarts on a silpat- or parchment-lined baking sheet until golden brown, about 15 minutes.
Whisk together the powdered sugar and milk until smooth.
Allow the pop tarts to cool completely then drizzle the tops with powdered sugar glaze.