Make the Biscuits

1. Heat the oven to 425 F (220 C) and position a rack in the center of the oven. Line a large baking sheet with parchment paper.
2. Cut the butter into 1/4-inch cubes or slices and put them in a small bowl. Put the cubed butter in the freezer.
3. Combine the flour, baking powder, soda, and salt in the bowl of a food processor. Pulse for a few seconds to blend.
4. Scatter the cubes of butter over the flour mixture and pulse just until the mixture resembles a coarse meal. You should have some visible pieces of butter that are the size of small peas.
5. Transfer the mixture from the food processor to a large bowl. Add the buttermilk and gently work it together until it is still crumbly but combined.
6. Turn the dough out onto a lightly floured surface and knead a few times to form a soft dough.
7. Roll the dough into a 3/4-inch thick rectangle.
8. Cut out biscuits with a round or square cutter. Gently re-roll the scraps. You should have 8 to 10 biscuits, depending on the size of the cutter.
9. Arrange the biscuits on the prepared baking sheet and brush the tops with evaporated milk, cream, or buttermilk.
10. Bake the biscuits until the tops are golden brown, about 15 minutes.

Make the Sausage Gravy

1. Put the sausage in a skillet and place it over medium-high heat. Cook, stirring and breaking up, until the sausage is no longer pink, 5 to 7 minutes. Reduce the heat to medium-low.
2. Sprinkle the flour over the sausage and continue to cook, stirring, for 2 to 3 minutes.
3. Gradually add the milk to the skillet while stirring constantly.
4. Continue to cook, stirring, for 5 minutes. Add extra milk as needed.
5. Taste and season with salt and pepper, as desired. Add a dash of red pepper flakes or cayenne pepper if using.