Mix Dry Ingredients. In a large bowl, combine the flour, baking powder, baking soda, and salt.
Cut in Butter. Add the cold butter and use a pastry cutter or your fingers to cut it into the flour mixture until it resembles coarse crumbs.
Add Buttermilk. Gradually add the buttermilk, stirring until just combined.
Form Biscuits. Turn the dough out onto a floured surface, gently knead, and pat it into a rectangle. Fold it over a few times to create layers, then cut out biscuits using a biscuit cutter.
Bake. Place the biscuits on a baking sheet and bake for 12-15 minutes, until golden brown.
Cook Sausage. In a large skillet over medium heat, cook the sausage until browned and cooked through.
Add Flour. Sprinkle the flour over the cooked sausage and stir to combine, cooking for about 1 minute.
Add Milk. Gradually add the milk, stirring constantly until the mixture thickens.
Season. Season with salt and pepper to taste, simmering for a few minutes until the gravy reaches your desired consistency.
Serve. Split the warm biscuits in half and ladle the sausage gravy over them.
Garnish. Optional – garnish with chopped fresh parsley for a burst of color and added freshness.