Mix cold unsalted butter, all-purpose flour, baking powder, and salt together
Add cold buttermilk to the mixture
Shape the biscuits and place on a baking sheet
Brush the top of each biscuit with beaten egg
Sprinkle with sea salt if desired
Bake at 375°F for 35 minutes until golden brown
Optional: Prepare dough and shape biscuits the night before, refrigerate overnight, and bake in the morning
