Whisk the flour, baking powder, and salt together in a large bowl. Add the cold cubed butter and use a pastry cutter or your fingertips to cut it in until the mixture resembles coarse, pea-sized crumbs. Work quickly so the butter stays cold. 350 g all-purpose flour, 1 Tbsp baking powder, 3/4 tsp salt, 113 g unsalted butter
Stir in the grated cheese and chopped chives. 200 g grated cheese*, 2 Tbsp fresh chives
Stir the sourdough discard into about half the milk to loosen it, then pour it into the flour mixture. Fold together with a spatula, then add more milk, 1 tablespoon at a time, until the dough just holds together when pressed. It should be shaggy and with some dry patches. 100 g sourdough discard starter, 100 g sourdough discard starter
Tip the dough out onto a lightly floured surface and push it into a rough rectangle about 7x10 inches (17x25cm).
Lift the bottom third of the dough and fold it into the middle. Fold the top third down over it, like folding a letter.
Turn the dough 90°, then press or roll it back out to 7x10 inches. Fold in thirds again.
Turn the dough 90° once more and press or roll out to 7x10 inches one last time.
Cut into 8 pieces for large scones or 10 pieces for small ones.
Place on a lined baking tray and refrigerate for at least 1 hour, or up to 24 hours.
When ready to bake, preheat the oven to 428°F/220°C (regular, not fan).
Brush the tops of the scones with milk and sprinkle over a little extra grated cheese. 2 Tbsp milk, Grated cheese
Bake for 12-16 minutes until deep golden brown. Smaller scones will need less time. Serve hot with a pat of butter.