Preheat oven to 400 degrees. Line a sheet pan with parchment paper.

In a medium bowl mix together the flour, baking powder, baking soda, and salt. Mix in the butter with a pastry cutter or a fork until mixture resembles coarse meal. Add the buttermilk and stir until the dough comes together in a ball.

On a lightly floured surface, gather the dough into a bowl and knead gently 6 times. Pat dough to about 1/2 inch thick. Cut dough into three inch rounds with a lightly floured cutter. Place on the prepared baking sheet about 2 inches apart. Brush with buttermilk.

Bake until golden brown, about 15-20 minutes. Transfer to a wire rack to cool.

While the biscuits are baking, prepare the gravy. Brown the sausage in a large saute pan set over medium high heat. Transfer browned sausage to a paper towel to drain.

Reduce heat to medium low and add butter and flour to pan and whisk together with remaining sausage drippings. Slowly add the milk a little at a time while whisking constantly, scraping bottom of pan with whisk to removed browned bits. Continue to cook, while whisking often, until gravy has thickened. Stir in salt and pepper and sausage. Simmer for about 5 minutes. Add additional salt and pepper to taste.

Serve warm biscuits with the gravy. Store leftover gravy in the fridge for up to 5 days. Store biscuits in an airtight container at room temperature for up to 3 days.