Rinse the seaweed and soak in 1 cup cold water for 10 minutes then drain. Soak mushrooms in hot water for 10 minutes, or until soft. Drain, retaining soaking water, and slice mushrooms thinly.
Heat oil in a pan and saute seaweed, mushrooms, tofu and carrot until the vegetables are tender. Add soy beans, dashi, soy sauce, mirin and mushroom water to cover and simmer, stirring occasionally, until liquid is absorbed.