Whisk together the flour, baking powder, and baking soda in a large mixing bowl
Cut or grate the butter into small pieces, and cut into the mixture using a pastry cutter or a fork. Cut until the mixture pieces are pea-sized.
Add the egg, buttermilk, and mix with a wooden spoon until just combined. If the mixture is too dry, add a little milk. Cover and refrigerate about 30 minutes.
Preheat your oven to 400F.
Flour a working surface and turn the dough out of the bowl. Press the dough using your hands until it's about an inch thick.
Using a biscuit cutter (or my favorite substitute, a mason jar) cut the biscuits and place on a baking sheet.
In a ramekin, beat the second egg and brush the tops of the biscuits.
Bake 12-15 minutes or until the tops are a nice golden brown. Cool on a rack.
Serve up with jam or honey, or alongside chili or chowder or lots of other ways!