Heat oven to 450°F. Whisk the 2 cups flour, baking powder, baking soda, and salt. Cut the cold butter into the dry mix until pea-sized pieces remain.

Stir in 3/4 cup buttermilk until a shaggy dough forms. Turn out, pat and fold 3 times, then pat to 3/4-inch thick. Stamp out biscuits with a 2 1/2-inch cutter, pressing straight down.

Place biscuits close together on a pan, brush with the extra buttermilk, and bake 12 to 15 minutes until golden. Cool on a rack for 5 minutes.

Meanwhile, brown the sausage in a skillet over medium-high heat, breaking it into small pieces and letting brown bits develop on the pan. Transfer the sausage to a plate, leaving the drippings.

Reduce heat to medium. Whisk the 1/4 cup flour into the drippings (add butter if dry) and cook 1 minute. Slowly whisk in the milk, then bring to a simmer. Stir in the cooked sausage and the 1 tsp black pepper. Simmer 1 minute until thick.

Split the warm biscuits and ladle the gravy over them. Finish with more black pepper.