For the S.O.S.
Heat a heavy sauce pan or cast-iron skillet with cooking oil/fat and sauté the sausage. Break it up into small chunks with a wooden spoon and allow it to brown slightly.
When the sausage is browned, remove it from the pan, reserving some of the cooking oil/fat, and set it aside.
Sauté the onion in the cooking oil/fat until it is translucent. When the minced onion is cooked, set it aside with the sausage. Drain any remaining oil/fat and return the pan to the heat.
Add the 4 tablespoons of butter and allow it to melt throughly. When the butter is melted, add the flour a small amount at a time and whisk it into the melted butter until combined and lightly browned. When ready, the mixture (called roux) should look like wet sand.
Add the milk and whisk until the gravy begins to thicken.
When you reach desired consistency, add the sausage and onion and season to taste with salt, black pepper and nutmeg. If the gravy becomes too thick, you can thin it by adding more milk or water.
Serve the warm sausage-gravy with the sourdough toast and fresh Italian parsley, watercress or arugula. The gravy is also great on biscuits or savory waffles!