In a large bowl, whisk the flour, salt, and sugar together.
Take the butter, and cut it into small cubes. Then, mix it with the flour mixture. The easiest way is to smush the butter with your hands, and then use a food processor to mix the rest. This should form a sand-like consistency.
Add 1 tbsp of water at a time, and mix. Once the dough just forms, that is enough water. Make sure not to over-add the water.
Put dough in cling wrap, and place in the refrigerator for 2 hours, or the freezer for 1 hour.
Preheat your oven to 360.
Take the dough out, and roll it out into 1/2 cm - 1 cm thick dough. Then with a knife, cut out two square pieces. Do this until all the dough is used.
Take two square pieces of the same length. Place a scoop of the cherry filling on the bottom piece. On the top piece, with a knife cut 3 small lines on top. Then, press the two pieces together and press a fork along the outside.
Mix the egg, and add it on top of the dough to form an egg wash. Then, sprinkle some sugar on top.
Bake for 18-22 minutes, or until golden brown.
