Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a large bowl, whisk together the flour, baking powder, baking soda, and salt.

Grate the cold butter directly into the flour mixture using a box grater. Place the bowl in the freezer for 5–7 minutes.

In another bowl, whisk together the cold buttermilk and egg.

In a small bowl, prepare the egg wash by whisking together the remaining egg and milk.

Remove the flour mixture from the freezer and gently toss the butter into the flour until evenly distributed.

Pour the buttermilk mixture into the flour mixture all at once. Stir gently until the dough just comes together.

Lightly knead the dough only a few times until it forms a rough ball. Avoid overmixing to keep the Buttermilk Biscuits light and flaky.

Turn the dough onto a lightly floured surface and pat it to about 3/4-inch thickness.

Cut biscuits with a 2½-inch biscuit cutter. Gather scraps gently to cut a few more biscuits.

Arrange biscuits on the prepared baking sheet.

Chill the baking sheet in the freezer for 5 minutes if the butter has softened.

Brush the tops with egg wash.

Bake for 10–15 minutes or until tall and golden brown.

Serve warm with butter, honey, or your favorite jam.