Makes 20 biscuits
- 1½ pounds / 680 grams all-purpose flour
- 1½ tablespoons / 27 grams baking powder
- 1½ tablespoons / 19 grams sugar
- 2 teaspoons / 12 grams fine sea salt
- 1½ teaspoons / 7.5 grams baking soda
- 2 cups plus 2 tablespoons / 510 grams chilled buttermilk
- 4 large egg yolks, divided
- 10 tablespoons / 140 grams chilled unsalted butter, diced
- 1 cup / 113 grams grated cheddar or Jack cheese
- ½ cup / 32 grams chopped fresh chives
- 2 tablespoons / 33 grams whole milk
Put the flour, baking powder, sugar, salt, and baking soda in a medium bowl and whisk to blend. Put the buttermilk and 3 of the egg yolks in a large measuring cup and whisk to blend. Cut the butter into the flour using 2 knives or a pastry blender until the mixture resembles coarse meal. Pour the buttermilk mixture into the flour and add the cheese and chives. Use a rubber spatula to gently mix everything together until all of the flour has been absorbed. Do not overwork the dough. You should be able to see bits of butter throughout the dough. Cover and chill for at least 30 minutes and up to 2 hours.
Turn the dough out onto a lightly floured countertop. Gently roll it out into a rectangle approximately ½ inch thick. Fold the top third down over the middle third and the bottom third up over the two layers, as you would fold a letter. Give the dough a quarter turn and repeat rolling and folding the dough. Wrap with plastic wrap and return to the refrigerator for 10 minutes to rest.
Preheat the oven to 375°F (190°C).
Put the remaining egg yolk and the milk in a small bowl and whisk with a fork until smooth. Take the dough out of the refrigerator, unwrap, and put it on a lightly floured countertop. Roll it out to a thickness of ½ inch and use a 2-inch biscuit cutter to cut out biscuits. Arrange them on a baking sheet, leaving 2 inches of space between each one. Brush the tops with the egg wash and bake for 8 minutes, or until they rise and turn golden brown.
Let rest for 5 minutes before serving.