In a large bowl, combine the flour and salt. Add the butter and use a pastry cutter or fork to cut them until the mixture resembles coarse meal. Add the water and vodka 1 tbsp at a time, until the dough begins to clump together. Don't overmix. You may not need all of the water/vodka.
Gently mold the dough into a ball. Cut in half and then press each into a flat disk. Cover with plastic wrap and refrigerate for 4 hours or overnight.
Once ready, lightly flour a clean surface. Take out 1/2 the dough and roll the crust down to 1/8" thick and 9x12" in size. Cut into 3x4" pieces so you'll end up with 9 rectangles. Using a spatula, transfer the rectangles to a parchment-lined baking sheet.
In a small bowl, whisk together the egg and milk. Brush the egg wash on each of the rectangles. Spoon a heaping tbsp of filling into the center of each rectangle, leaving 1/2" of space around the edge.
Take out the second piece of dough and roll out to the same size as the first. One at a time, place a second rectangle on top of the 9 assembled ones. Use your fingers to press around the seems and then use a fork to form the edges. Poke holes in the tops of each filled pastry to allow steam to escape.
Place the pop tarts in the fridge for 30 minutes.
Preheat oven to 350°F. Bake the pop tarts for 25-30 minutes or until lightly browned, rotating halfway through. Let the pop tarts cool on the pan for 5 minutes before transferring to a wire rack to cool completely before glazing.