Line a baking sheet with parchment paper or a silicone baking mat. Preheat oven to 425°F.

Add all the dry ingredients to a medium-sized mixing bowl and whisk to combine.

Freeze the stick of butter for at least 20 minutes. Using a box grater or cheese grater, grate the frozen butter directly into the dry mix using the larger holes. With two forks, mix the butter into the dry mixture, fully coating the butter.

In a small bowl, whisk together the buttermilk, milk, and egg; reserve 1 Tbsp of the mixture for the egg wash.

Top the flour mixture with the egg mixture. Using two forks, mix until a rough dough forms.

Very lightly flour the counter and add the dough. Gently knead the dough into a round. With a floured rolling pin, roll the dough out to about 1 inch thick. Cut out circles with a 2 1/4-inch cookie cutter. Press straight down without twisting the cutter. Re-roll the dough as necessary, handling it as little as possible to keep the butter from getting warm.

Place the scones onto the prepared baking sheet and brush the top of the scones with the reserved egg mixture.

Bake for 12-15 minutes till the scones are golden brown on top.

Remove and let cool slightly.