Sift together flour, sugar, baking powder and salt
Combine your milk and lemon juice (or use buttermilk)
Grate cold butter into the dry ingredients (using a scale makes this very easy)
Toss the ingredients together to coat all the butter with the flour mixture
Make a well in the center of your dry ingredients and then add in the cold buttermilk and lemon zest. Pull the dry ingredients towards the center and then mix with your hands in the shape of a "claw" or fork until the dough forms a loose sticky ball. Do not over-mix.
Flatten the dough roughly with your hands or rolling pin to about 2" in height. Fold in half. This will be messy! Flatten dough once again.
Rotate your dough 45º and fold in half again. Repeat 5-7 times. If the dough becomes stretchy, place it in the fridge for 10 minutes to relax the gluten.
Use a 4" round biscuit cutter make your biscuits. Press striaght down and lift straight up. Do not twist.
Place the biscuits on a parchment lined sheet pan with about 1/4" of space in between the biscuits and brush with milk or egg wash on top. Do not brush the sides. Sprinkle with sanding sugar for extra crunch and sweetness if desired.
Bake at 375° F for 20-25 minutes or until they are golden brown. Rotate the pan half way through baking for even browning. Let them cool on a cooling rack.