Slice the onion thinly and cut the root off the shimeji mushrooms, then separate them.

Cut the bacon into thin strips.

Mix the egg and grated cheese in a bowl.

Heat butter in a frying pan, then add onion, bacon, and shimeji mushrooms. Sauté over medium heat until the onion softens.

Add milk, water, salt, and consomme powder to the pan. Bring to a boil, then add spaghetti (broken in half) and stir.

Cover the pan and cook over low heat for 2 minutes longer than the package instructions.

Dissolve miso into the mixture, turn off the heat, and add the egg mixture. Stir quickly to combine.