It’s best to make the dough for these biscuits a day before you want to bake them (or the dough can be frozen). The combination of yeast, which needs time to slowly rise, and baking powder plus baking soda makes this the fluffiest biscuits imaginable.
Makes 18-24 biscuits.
Stir the flour, sugar, yeast, baking powder, salt and baking soda in a large mixing bowl, or in the bowl of a stand mixer fitted with the paddle attachment. Add the butter and cut in (use a pastry cutter if mixing by hand) until no large pieces of butter are visible. Stir in the cheese and chives and then add the buttermilk mixing until the dough comes together. Shape the dough into a disc, wrap in plastic wrap and chill for at least 6 hours up to 24 hours.
Line a baking tray with parchment paper. Unwrap the dough and roll it out on a lightly floured surface to just under an inch (25 mm) thick. Use a 2-inch (5 cm) cutter to cut out biscuits, re-rolling any scraps. Cover the tray with a tea towel and let this sit on the counter for 60 minutes.
Preheat the oven to 400°F (200°C). Brush the tops of the biscuits with the eggwash and bake for about 15 minutes, until they are golden brown on the bottom (they will brown only lightly on top). Let the biscuits cool for 10 minutes, but they are delicious enjoyed warm, the day they are baked.