In a medium size bowl add all-purpose flour, pastry flour, baking powder, and salt. Stir together.
Shred the butter with a cheese grater (the butter must be as cold as possible), and add to the bowl. Using a fork, cut the butter into the flour mixture until crumbly.
Form a well in the middle of the bowl, and add the milk. Stir the flour mixture into the milk until a dough forms.
Sprinkle a light dusting of flour on a cutting board. Transfer the dough to the cutting board. Knead the dough a few times then roll it with a rolling pin so that it’s about an inch thick.
Cut the dough into rounds with a biscuit cutter. Grease a cookie sheet or baking pan with butter.
Spaced out evenly, lay the biscuits on the baking pan and set aside for just a moment while making the egg wash.
For the Egg Wash: In a small bowl, add the egg white (separate the egg white from the yolk by cracking the egg in half, and slowly tilting the half of the egg with the yolk in it toward a small bowl so just the egg white pours out). Discard the yellow part of the yolk.
To the bowl, add sugar, water, and whisk together. Brush the egg wash over the top of the biscuits.
For the Topping:
Sprinkle sugar on the top of each biscuit. Bake until the tops of the biscuits are a light golden color (about 12 to 15).
Serve warm with butter or delicious Apple Cinnamon Toast Butter or honey.
Separate the egg white from the yolk by cracking the egg in half, and slowly tilting the half of the egg with the yolk in it toward a small bowl so just the egg white pours out.