Cut 2 sticks of butter into small pieces. Place on plate and refrigerate.
Cut the other ½ stick of butter into small pieces. Add to mixing bowl with 2 cups of flour and use a pastry cutter or two butter knives to blend. Should resemble coarse crumbs/sand.
Add refrigerated butter cubes to flour mixture. Toss to coat with flour. DO NOT cut in with pastry cutter.
Mix cold water and salt together. Add to bowl. Mix until water has been absorbed and a rough dough forms. Use hands or Danish dough whisk to mix dough. Dough won't look completely formed and there will be butter chunks, and that's okay.You may add an extra tablespoon of water (if needed) to help the dough come together. It will be crumbly, but you shouldn't a lot of flour leftover in the bowl.
Dump dough onto a piece of plastic wrap. Place a second piece of plastic wrap on top and press with hands to flatten. Roll with a rolling pin until butter has flattened and dough is flat across the top.This step will help press the butter into the flour.
Remove plastic wrap and place dough onto floured surface. Flour hands to prevent dough from sticking and form dough into a ball. Flatten slightly with hands into a disc shape.
Cover rolling pin with flour to prevent butter from sticking and roll dough into a 6" x 18" rectangle. Fold dough into thirds, like a business letter.
Wrap dough in plastic wrap and refrigerate for 1 hour.
When dough has refrigerated for 1 hour, preheat oven to 400 degrees.
Flatten dough on floured surface by pounding with rolling pin a few times. Roll out until dough is ¼" thick. Trim edges of dough to a 10" x 20" rectangle. Cut into 8 (5 inch) squares.
Add a small amount of apple pie filling to the center of each pastry square.
Fold pastry in half (diagonally). Press down with fingers. Press fork around the edge of each pastry to seal. Place turnovers onto ungreased baking sheet or baking sheet lined with parchment paper.
Mix egg with 1 Tbsp. water to create an egg wash. Brush over turnovers and sprinkle with sugar (I use coarse sugar sprinkles).
Bake for 22-24 minutes, or until golden brown. Cool on a wire rack. These are delicious served with a scoop of vanilla ice cream.