Brown the sausage in a large skillet over medium heat, breaking it into crumbles.
Stir in the butter until melted and coats the sausage.
Sprinkle flour over the sausage. Cook, stirring often, for about 2 minutes.
Gradually pour in the milk while whisking to prevent lumps.
Bring to a gentle simmer. Cook, stirring, until thick and creamy, 5–7 minutes.
Season with salt, black pepper, red pepper flakes, garlic powder, and onion powder.
Taste and adjust seasoning. Thin with a splash of milk if too thick. Serve warm.