Preheat the oven to 350 degrees F. Line a baking sheet with a silicon mat or parchment paper. Set aside.
Carefully unroll the pie crust dough. Using a rolling pin, roll out any rough spots to flatten them. Use a 3-inch round cookie cutter to cut out 8 circles of dough. Re-roll the remaining pie crust dough and cut out more circles. (I usually get about 20 total.)
Place the pie crust circles onto the prepared baking sheet. (You will need to cook in batches.) In a small bowl, whisk together the egg and water. Brush this egg wash around the edge of each circle.
Spread 1/2 teaspoon of pizza sauce on one half of each circle, making sure not to go over the egg wash. Then place 1 teaspoon of mozzarella cheese over the pizza sauce and then 3-4 mini pepperoni over the cheese.
Fold the bare side of the pie dough over the top, making a half-circle. Gently press the edges together with your fingers. Use a fork to crimp the edges together so they are sealed.
Brush each pizza bite with some of the egg wash. Then sprinkle the top with garlic salt and Parmesan cheese.
Bake for 15 to 17 minutes, or until golden brown. Remove from the oven and serve warm with extra pizza sauce for dipping.