In a large mixing bowl, combine 2 cups of all-purpose flour, 1 cup of sourdough discard, 1 tablespoon of sugar, and 1 teaspoon of salt. Cut in ½ cup of cold unsalted butter until the mixture resembles coarse crumbs. Gradually add 3-4 tablespoons of cold water, mixing until a cohesive dough forms. Knead gently for 1-2 minutes, wrap in plastic wrap, and chill in the refrigerator for 30 minutes.

Once chilled, flour your work surface and roll out the dough to 1/8-inch thickness. Cut the dough into squares approximately 4x4 inches. Place half of the squares on a parchment-lined baking sheet.

Spoon about 1 tablespoon of your favorite jam or jelly onto the center of each dough square, leaving a small border around the edges.

Take the remaining squares and gently place them on top of the filled squares. Press down around the edges to seal, then crimp with a fork and make small slits on top.

Preheat your oven to 400°F (200°C). Brush the tops of the sealed tarts with a beaten egg and bake for 10-12 minutes until golden brown.

While the tarts cool, whisk together 1 cup of powdered sugar and 2-3 tablespoons of milk until smooth. Adjust consistency as needed.

Drizzle the glaze over the cooled pop tarts and allow to set before serving.