To a sauté pan, set over medium heat, melt 1 tablespoon of butter. Throw in the minced shallot and Italian sausage. Using a wooden spoon, break up the sausage into crumbles; and cook the sausage for about 5 minutes, until brown in color. Remove the sausage crumbles with a slotted spoon and set them aside. Note: My sausage wasn't particularly greasy--it left about 1 tablespoon of fat in the pan. If for some reason yours expels a large amount, remove some so you have about three tablespoons of fat left.
Add more butter, if needed (I added 3 tablespoon of butter). When the butter has melted, add the flour and mix until combined. Pour in the milk and stir until the gravy has thickened, about 2 to 3 minutes. If the gravy becomes too thick, don't be shy about adding a splash of milk to thin it out a bit. Next, stir in the the pepper and Dijon mustard. Add a bit more mustard or pepper, if you like. And then, salt to taste. I added about 1 1/2 teaspoons of salt.
To serve, divide the biscuits amongst plates and spoon the gravy atop the biscuits. This is good living!
If you'd like to make this the night before, feel free to make it per the instructions and then transfer it to the refrigerator. To reheat, add a splash of milk, place over medium low heat and stir until warmed.