Wash and cut the lettuce and spinach. Cut the cucumber and tomatoes into cubes. Cut the tofu into cubes of the same size. Boil the eggs until waxy, peel and cut in halves. Cut the spring onions diagonally into oval rings. Bring the brown seaweed to the boil in a little water and let it soak for ten minutes. Then strain and throw away the soaking water.
Mix the mirin, rice vinegar and soy sauce into a marinade and mix well with the lettuce, diced tomatoes and cucumber. Top with the tofu, seaweed, egg halves and spring onions.