Thinly slice the onion and cut the bacon into strips.

Heat butter in a frying pan, add the onion, and sauté over medium heat until softened. Add the bacon and stir briefly.

Add the sauce ingredients (milk, water, salt, consomme) to the pan and bring to a boil. Break the spaghetti in half and add it to the pan, stirring to combine.

Cover the pan and simmer on low heat, stirring occasionally, for 2 minutes longer than the package cooking time.

Turn off the heat, add grated cheese and black pepper, and mix well.