2 1/2 cups all-purpose flour, plus extra for rolling
1 tablespoon baking powder
1 teaspoon kosher salt
1/2 teaspoon baking soda
1/2 cup very cold unsalted butter, cubed
3/4 cup cold buttermilk
1/4 cup honey
1 large egg, separated
1 tablespoon milk
Preheat the oven to 425°F. Line a baking sheet with parchment paper.
In a large bowl, combine the flour, baking powder, salt, and baking soda. Toss the chunks of cold butter into the flour mixture. Using clean hands or a pastry blender, work the butter and flour together until it resembles coarse crumbs, with butter pieces no larger than a pea.
With a wooden spoon, slowly work in the buttermilk, honey, and egg yolk until a dough forms and is slightly sticky. Turn the dough onto a lightly floured work surface and sprinkle a little more flour on top of the dough.
Using a floured rolling pin, roll the dough out into a 1/2-inch-thick rectangle, then fold dough into a letter fold. Repeat the process 2 more times. Wrap the dough in plastic wrap and refrigerate for about 15 minutes.
Roll the dough out to about a 3/4-inch thickness. Using a 2-inch round cookie cutter, cut the biscuits and arrange them 1 inch apart on the prepared baking sheet. Gather and reroll the scraps once and cut out additional biscuits. Discard any scraps leftover after rerolling. Chill the tray of biscuits in the refrigerator for at least 30 minutes.
In a small bowl, whisk the egg white and milk for the egg wash. Brush the dough with the egg wash before baking.
Bake until the tops are golden brown, 10 to 12 minutes. Allow the biscuits to cool for 5 minutes before serving.
Store leftover biscuits in a sealed bag for up to 5 days at room temperature or up to 2 weeks in the freezer.