Preheat oven to 350 degrees Fahrenheit. Line a large baking sheet (or 2) with parchment paper.

Combine the dry pie dough ingredients (flour and salt) in a large mixing bowl and mix well.

Combine the beaten egg, water, vinegar, and sourdough discard in a separate large bowl.

Cut the shortening (butter) into the dry ingredients and then add in the wet ingredients to the flour mixture.

On a lightly floured work surface, fold dough into itself until all flour is combined.

Roll the dough into a rectangle and trifold it into itself 3-4 times.

Add flour to the work surface and roll the dough out into a 18x20 inch rectangle.

Divide the dough into 12 equal parts - square portions.

Add the apple pie filling to half of the dough square (in a triangle shape).

Sprinkle the brown sugar evenly across the pie filling portions (if using store bought or sliced apples).

Fold the dough into half to form a triangle shape and seal the edges with a fork.

Brush the tops of the triangles with the egg wash (egg yolk) using a pastry brush.

Bake the apple turnovers for about 25-30 minutes our until golden brown.