How to Make It
In a nonstick skillet over medium heat, cook the sausage, stirring, until browned and cooked through, about 4 minutes. Let cool to room temperature, then crumble by hand until the pieces are the size of peas. Reserve.
Melt the butter in a saucepan over medium heat. Add the flour and whisk until a roux forms. Continue to cook, whisking constantly, until the roux turns a light gold and gives off a nutty aroma, 3 to 4 minutes. Remove from the heat and set aside.
Warm the milk in a medium saucepan over medium heat for about 2 minutes. Add the milk to the roux and cook over medium heat, whisking often, until thickened, about 5 minutes. Add the cooked sausage and stir until fully combined, followed by the red pepper flakes. Season with salt and black pepper. Keep warm on the stovetop for up to an hour. Serve warm.