Preheat your oven to 450°F (232°C). Line a baking sheet with parchment paper or lightly grease it.

1. In a large bowl, whisk together the flour, baking powder, salt, and sugar. Add the cold, cubed butter and use a pastry cutter, two forks, or your hands to cut the butter into the flour until the mixture resembles coarse crumbs with pea-sized pieces of butter.
2. Make a well in the center of the flour mixture and pour in the buttermilk. Stir gently with a spoon until the dough just comes together. Be careful not to overmix.
3. Turn the dough out onto a lightly floured surface and gently knead it 2-3 times until it holds together. Pat it into a rectangle about 1 inch thick. Use a biscuit cutter or a glass to cut out biscuits (you should get about 8-10 biscuits, depending on the size).
4. Place the biscuits on the prepared baking sheet, close together for soft sides or spaced apart for crispier sides. Bake in the preheated oven for 12-15 minutes or until golden brown on top.
5. Once baked, remove from the oven and set aside while you prepare the gravy.
6. In a large skillet, crumble the sausage and cook over medium heat until browned and cooked through, about 5-7 minutes. Stir occasionally to break up the sausage into small pieces. Remove the sausage from the pan and set aside, leaving some of the rendered fat in the pan.
7. To the same skillet, add 1/4 cup of flour to the sausage fat and cook for 1-2 minutes over medium heat, stirring constantly. This creates the roux, which will thicken the gravy.
8. Slowly whisk in the milk, making sure to break up any lumps in the flour. Bring the mixture to a simmer, stirring constantly.
9. Once the gravy has thickened, return the cooked sausage to the skillet and stir to combine. Season the gravy with salt, pepper, garlic powder, and red pepper flakes, if using. Let it simmer for another 2-3 minutes until the gravy is thick and creamy.
10. Pour the sausage gravy over the warm biscuits and serve immediately. Garnish with extra black pepper or chopped herbs like parsley if desired.