Slice the onion thinly and trim the base of the maitake mushrooms, then separate them.

Heat olive oil in a frying pan, add the beef and onion, and sauté until the beef changes color.

Add the maitake mushrooms and sauté for 2–3 minutes.

Add water and the seasoning ingredients (sake, salt, ketchup, Worcestershire sauce, consomme, and pepper). Bring to a boil, then add the spaghetti, breaking it in half.

Cover and cook over medium heat for the time indicated on the spaghetti package. Then cook uncovered for 5 minutes to reduce the liquid.