Cook the crumbled sausage in a large skillet over medium heat until it is fully browned and broken into small pieces. The meat should lose its pink color, smell savory, and leave flavorful drippings in the pan.

Sprinkle in the flour and stir it through the sausage until the drippings absorb it and no dry patches remain. After about a minute or two, the mixture should look pale golden, a bit like peanut butter, and smell lightly toasted instead of raw.

Pour in the milk gradually while whisking or stirring constantly to smooth out the roux as it loosens. The mixture will first look thin, then turn creamy and uniform as the milk fully blends with the flour and sausage fat.

Keep cooking over medium heat until the gravy thickens and starts to bubble gently. You should feel more resistance on the whisk or spoon, and the gravy should coat the back of it without looking gluey.

Taste and season with salt and black pepper. The finished gravy should taste savory and peppery, with enough seasoning to wake up the milk and sausage.

Spoon the hot gravy over the biscuits and serve right away, then cool any leftovers before covering and refrigerating. The gravy is at its best when it is hot, glossy, and loose enough to spread over the biscuit halves.