Blueberry Pop Tarts

In a large mixing bowl, combine flour, cold butter, shortening, and salt. Using a pastry cutter or your hands, work the butter into the flour until it resembles coarse crumbs. Slowly add in the ice-cold water, a tablespoon at a time, mixing until the dough just comes together. Divide the dough into two equal discs, wrap in plastic wrap, and refrigerate for at least 2 hours.
In a small bowl, combine the cornstarch and water. Stir until the cornstarch dissolves, then mix it into the blueberry jam. Set aside.
Flour your countertop and roll out one disc of dough at a time. Roll it into a rectangle about 12 inches long. Trim any rough edges and cut into 3x4.5-inch rectangles. Place half of the rectangles on a parchment-lined baking sheet. Top each with 1-2 tablespoon of blueberry jam, leaving a border. Brush the edges with egg wash.
Place the remaining dough rectangles over the jam-covered pieces. Press the edges to seal, crimping them with a fork to secure. Poke a few vent holes in the top of each pop tart. Brush with egg wash.
Preheat your oven to 350°F (175°C). Bake the pop tarts for 19-23 minutes or until golden brown. Allow to cool on a wire rack.
Pulse the freeze-dried blueberries in a food processor until finely ground. In a bowl, combine the powdered sugar, heavy cream, and blueberry jam, stirring until smooth. Spoon the glaze over the warm pop tarts or let them cool before glazing.