01 - Preheat the oven to 425°F and line a baking sheet with parchment paper.
02 - Combine the flour, baking powder, baking soda, salt, and sugar in a large bowl; whisk until evenly blended.
03 - Add cold, cubed butter to the dry ingredients. Use a pastry cutter or fingertips to cut the butter into the flour mixture until it resembles coarse crumbs.
04 - Pour in cold buttermilk and stir gently just until a shaggy dough forms; avoid overmixing to maintain flakiness.
05 - Turn the dough onto a floured surface; pat into a 1-inch thick rectangle. Fold the dough in half and pat again; repeat this folding two more times to create flaky layers.
06 - Using a 2.5-inch round biscuit cutter, cut out biscuits and place them close together on the prepared baking sheet for softer edges.
07 - Brush biscuit tops with extra buttermilk and bake for 12 to 15 minutes until golden brown; remove and allow to cool slightly.
08 - While biscuits bake, crumble and brown the sausage in a large skillet over medium heat until fully cooked, about 6 to 8 minutes.
09 - Sprinkle flour over the cooked sausage and stir continuously for 1 to 2 minutes to eliminate raw flour taste.
10 - Gradually pour in the milk while stirring to prevent lumps. Add black pepper, salt, and cayenne pepper if using.
11 - Simmer the mixture, stirring frequently, until the gravy thickens, approximately 5 to 7 minutes. Adjust seasoning to preference.
12 - Split warm biscuits and spoon generous amounts of hot sausage gravy over each. Serve immediately.