Set your oven rack in the center and heat to 425°F. Line a baking sheet with parchment. Warm milk for gravy in a small saucepan, then keep off heat.

In a large bowl, whisk flour, baking powder, baking soda, and salt until evenly blended. This aerates the mixture and boosts rise.

Drop cold butter cubes into the flour and work with a pastry cutter or two knives until pea-sized lumps form.

Make a well in the center, pour in buttermilk, and stir gently with a wooden spoon until the dough just comes together.

Turn dough onto a lightly floured surface, pat into a ¾-inch thick rectangle, then fold it over itself twice for layers. Cut rounds with a biscuit cutter.

Brush tops with a little milk, sprinkle with sea salt, then bake for 12–15 minutes until golden brown.

Crumble sausage in a skillet and cook until no pink remains, stirring occasionally.

Sprinkle flour over sausage, stir for 1 minute. Gradually whisk in warm milk, scraping up browned bits.

Bring gravy to a gentle bubble, then simmer on low for 5–7 minutes, stirring occasionally, until thickened.

Stir in black pepper and cayenne. Split warm biscuits, ladle gravy over the top, and garnish with parsley or chives.