Pre-heat oven to 400F (200C) and line a cookie sheet with parchment paper.
In a small bowl beat together the egg and milk, set aside. 1 large egg, 3 tablespoons milk
In a large bowl whisk together the flour, baking powder, salt, sugar and zest. Add the cold butter and mix to form coarse crumbs. Add the egg mixture and mix with a fork or spatula just until combined (about 15 or 16 stirs). 1 cup all purpose flour (125 grams), 1 teaspoon baking powder, 1 pinch salt, 1 tablespoon sugar, 1 tablespoon orange zest, 2 tablespoons butter (cold)
Drop the batter by heaping tablespoons (6 mounds) on the prepared cookie sheet. Bake for approximately 15-18 minutes or until lightly golden (a little darker on the edges). Move to a wire rack to cool. Enjoy!
Notes
If you find the dough too dry then add ½ tablespoon of milk at a time. But it should be fine with these measurements.If you want to add extras such as chocolate chips or dried fruit (about ¼ cup) then toss them into the mixture with the egg mixture.
How to store them
The baked cooled biscuits should be kept at room temperature in an airtight plastic bag. They will keep for up to two days.The biscuit dough can be made in advance and stored for up to three days in the fridge. Or if you want to freeze the unbaked dough, then freeze the formed unbaked biscuits for a few hours or until firm and then move to a freezer safe bag or container.They can be baked straight from the freezer, just increase the baking time to about 4-5 minutes.The cooled baked biscuits can also be frozen, freeze in a container or bag. The raw dough will last up to three months in the freezer.