Cut the tofu into bite-sized pieces. Thinly slice the onion, cut shungiku into 4cm pieces, and trim the base of maitake mushrooms, separating them by hand.

Heat salad oil in a frying pan over medium heat. Add the beef and sauté briefly. Mix in the seasoning ingredients (sake, mirin, sugar, soy sauce) and add the tofu. Simmer for about 2 minutes over medium heat.

Add onion, maitake mushrooms, and water. Cover with a lid and simmer over medium heat for about 5 minutes until the onion becomes translucent and the mushrooms soften.