In a large bowl, combine flour, salt, and sugar. Add butter and mix with your hands or a pastry cutter until crumbly. Add water a little at a time until the dough forms a ball. Don’t add more than 1 Tablespoon at a time. More flour can be mixed in if too much water is added.
Divide the dough in half. Form dough into 2 flat discs and wrap with plastic wrap. Freeze for 10 minutes or refrigerate for at least 30 minutes.
Roll and cut the dough
Take one dough disc out and roll to ¼ inch thickness on a floured surface.
Cut into 3 inch by 4 inch rectangles. This will make 9 rectangles. Repeat with the other dough disc. You will have 18 rectangles total.
Lay 9 of the rectangles on a parchment paper lined baking sheet.
Make the filling and assemble
Combine brown sugar, cinnamon, and flour together in a small bowl.
In another small bowl, whisk together the egg and milk to make the egg wash. Brush the egg wash over each of the 9 dough rectangles on the parchment paper.
Put a Tablespoon of the cinnamon sugar filling on each, leaving a ¼ inch space around the edges. Place the remaining 9 dough rectangles on top and seal with the tines of a fork around the edges.
Brush the tops with the egg wash and poke the centers with the fork a couple times to let steam escape while baking. Refrigerate for at least 30 minutes before baking.
Baking and icing
Bake at 350°F for about 25-30 minutes, until they are lightly browned. Cool before icing.
Make the icing by combining powdered sugar and cinnamon together in a small bowl. Add 1 Tablespoon of milk and stir. Add 1-2 teaspoons milk as needed to make a smooth icing that is still slightly thick. Use a spoon to spread the icing on top of the pastries.
These can be stored in a sealed container at room temperature for 2-3 days or in the refrigerator for a week. Reheat in an oven or toaster oven at 350°F for a couple minutes.