Preheat oven to 450°F and spray an 8x8 baking dish with nonstick spray.
In a medium bowl, whisk together flour, baking powder, sugar, and salt.
Pour in the buttermilk and stir until just combined (do not overmix).
Pour the melted butter into the prepared baking dish.
Spoon the biscuit dough on top of the melted butter and spread it out evenly.
Use a knife to score the dough into 9 equal squares.
Bake uncovered for 25-28 minutes until golden on top.
Let cool for 5 minutes. Slice through the pre-scored lines and remove biscuits.
Slice each biscuit and fill with a sausage patty and cheddar cheese to make breakfast sandwiches.