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

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

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

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

In a separate small bowl, whisk together the egg wash ingredients. Refrigerate until ready to use.

Remove the flour mixture from the freezer and gently toss the butter into the flour using your fingertips until the mixture resembles coarse crumbs.

Pour the buttermilk mixture into the flour mixture all at once. Stir just until combined.

Lightly knead the dough until it comes together without overworking it.

Transfer the dough to a lightly floured surface and gently press it into a 3/4-inch thick rectangle.

Cut using a 2½-inch biscuit cutter to make about 6 biscuits. Gather the scraps once to make approximately 2 additional biscuits.

Arrange the biscuits on the prepared baking sheet. If needed, chill the tray in the freezer for 5 minutes to keep the butter cold.

Brush the tops with the egg wash.

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

Serve warm with butter, honey, fruit preserves, or your favorite breakfast spread.