Blueberry Toaster Pastries

Name: Blueberry Toaster Pastries
Ingredients: 3 tablespoons sugar; 2 teaspoons cornstarch; Pinch of kosher salt; 5 ounces fresh blueberries (1 cup); Grated zest of 1/2 lemon; Unbleached all-purpose flour, for dusting; 1 package (14 ounces) all-butter puff pastry, thawed; 1 large egg; Sugar/Blueberry Glaze (recipe follows) and purple sprinkles (optional), for decorating; ¼ cup freeze-dried blueberries (optional; omit to keep glaze white); 1 ¼ cups confectioners' sugar; ¼ teaspoon pure vanilla extract