Preheat oven to 400°F (200°C) and grease a 9×9 inch baking dish.
Whisk together flour, baking powder, and salt in a large bowl.
Cut cold cubed butter into dry ingredients using a pastry cutter or fingers until mixture resembles coarse crumbs with pea-sized pieces, about 2-3 minutes.
Stir in buttermilk, cooked sausage, and shredded cheddar just until combined, about 15-20 stirs maximum. Do not overmix.
Spread batter evenly into prepared baking dish.
Pour melted butter evenly over the top of the batter.
Bake for 20-25 minutes until top is golden brown and a toothpick inserted in center comes out clean, or internal temperature reaches 190°F.
Let cool for 5 minutes before cutting into squares and serving warm.
Notes
Use very cold butter and buttermilk for flakiest texture. Keep ingredients chilled until ready to use.
Drain cooked sausage thoroughly on paper towels to prevent greasy biscuits.
Substitute Monterey Jack or pepper jack cheese for variation. Add cayenne pepper for heat.
These freeze well for up to 2 months. Reheat from frozen at 375°F for 12-15 minutes.