Instructions

• In a medium-sized mixing bowl, whisk the flour, sugar and salt. Grate the cold vegetable shortening, using a cheese grater, into the flour mixture. Use a bench scraper or a pastry cutter to cut the vegetable shortening into the flour until it forms large crumbles.
• Add the sourdough starter discard and vinegar to the mixture and use a fork to bring the dough together. Use your hands to bring the mixture into a cohesive ball and press into a rectangular shape. (Add a teaspoon of cold water if the mixture is too dry.)
• Wrap the dough in plastic wrap and use a rolling pin to flatten the dough and smooth the edges. Let the dough chill in the fridge for at least one hour. (Up to 24 hours) Chilling the dough is essential because it allows the gluten to relax, which results in a more tender crust. Cold dough is also easier to roll out, preventing the shortening from melting and creating a greasy pastry.
• Preheat your oven to 350°F (177°C) and line a baking sheet with parchment paper.
• Roll the dough into a rectangle, with a 1/8" thickness, on a lightly floured surface. Cut the dough into 4 long strips. Brush the edges with the egg wash.
• Add 2 tablespoons of filling to one side of each rectangle and fold the dough over itself. Use a fork to press and seal the edges. Brush the egg wash over the top of each pop tart.
• Place the pop tarts onto the baking sheet and bake for 25-30 minutes or until the crust is golden brown. Remove from the oven and transfer the baked pop tarts to a cooling rack.
• In a small bowl, whisk the powdered sugar and water together until thick and smooth. Pour onto each pop tart and sprinkle with coarse sugar or sprinkles. These sourdough pop tarts are best enjoyed fresh.