Preheat the oven to 425°F and line a cookie sheet with parchment paper.
In a large bowl, combine the flour, baking powder, sugar, and salt.
Grate the cold butter into the flour mixture and work it in quickly until coarse crumbs form.
Stir in the buttermilk until a loose dough forms.
Flour your surface and place the dough on it. Gently work the dough together with your hands.
Shape the dough into a rectangle about 1 ½ inches thick. Use a round biscuit cutter to cut out 4 biscuits.
Rework the dough into a smaller 1 ½ inch thick rectangle and cut out 2 more biscuits.
Place the biscuits on the prepared baking sheet. Brush the tops with melted butter if desired.
Bake for 12-15 minutes until golden brown.
To make the gravy, cook and crumble the sausage in a large skillet over medium heat (do not drain off any grease).
Add the flour to the pan and stir it into the sausage.
Gradually pour in the milk, stirring constantly until the mixture comes to a boil and thickens.
Season with salt and pepper to taste, with a heavier hand on the pepper.
Serve the gravy over the warm biscuits.