Remove one baking sheet of pastry rectangles from the refrigerator. These will be the bottoms of your pop tarts. Brush egg wash over the entire surface of each rectangle. Place a heaping Tablespoon of the filling into the center of each rectangle and spread it around with the back of a spoon, leaving a 1/4-inch border around the edges.
Remove the 2nd baking sheet of pastry rectangles from the refrigerator. These will be the tops of your pop tarts. Brush egg wash over the entire surface of each top rectangle, then place each top rectangle, egg-wash-side-down, on the filling-topped bottoms. Use your fingertips to press firmly around the pocket of filling, sealing the dough well on all sides. Reserve remaining egg wash.
Using a toothpick, poke 6 to 8 holes in the tops of each filled pastry to allow the steam to escape. You can, instead, use a knife to make a few small slits. Seal the edges tightly by crimping with a fork. Refrigerate the filled pop tarts, uncovered, for at least 20 minutes and up to 1 hour.
Preheat the oven to 350°F (177°C). Once the unbaked pop tarts have chilled for 20 minutes, remove from the refrigerator and brush the tops with the remaining egg wash.
Bake for 25–30 minutes or until golden brown, rotating the pan halfway through baking. Let the pop tarts cool on the pan for about 5 minutes, then transfer to a cooling rack to cool completely before icing.