Preheat oven to 450°F (230°C). In a large bowl, whisk together 2 cups flour, baking powder, and 1/2 tsp salt.

Cut cold butter into small cubes. Using a pastry cutter or fingers, work butter into flour mixture until it resembles coarse crumbs.

Make a well in center and pour in buttermilk. Stir just until dough comes together (do not overmix).

Turn dough onto floured surface, pat into 1-inch thick rectangle. Fold dough over itself 3-4 times for layers. Cut into squares or circles.

Place biscuits on ungreased baking sheet. Bake 12-15 minutes until golden brown. Let cool slightly.

While biscuits bake, cook sausage in large skillet over medium heat until browned, breaking into small pieces.

Sprinkle 3 tbsp flour over sausage, stir to coat. Cook 1 minute to remove raw flour taste.

Gradually whisk in milk. Bring to simmer, stirring constantly until gravy thickens (about 5 minutes). Season with black pepper, salt, and red pepper flakes.

Split warm biscuits in half. Place bottom halves on plates, smother with gravy, then top with biscuit tops. Serve immediately.