Put the flour, icing sugar and salt in a large bowl (or in a food processor).
Rub in the cold cubed butter until it resembles bread crumbs.
Mix together the egg yolks and water and add to the dry ingredients.
Mix in until a dough forms. It doesn't take long.
Wrap the pastry in cling wrap and refrigerate for 30 minute to allow the gluten to relax. (you can freeze the pastry at this point)
Make the filling: Mix the brown sugar, cinnamon, and flour together in a small bowl. Set aside.
Roll out your dough on a floured surface until 1/4 inch thick.
With a pizza cutter or knife cut your pastry to 3inch x 4inch rectangles. You will need 2 for each pop tarts.
Spoon your filling into the center of the piece of pastry
Egg wash your pastry, this will help the 2 pieces stick together and give your pop tart a lovely golden color. Prick the top with a fork to release steam while baking
Bake at 400oF (200oC) for 22-25 minutes or until golden brown.
Mix the icing ingredeint together and spoon over the pastry.