Cut the tofu and mushrooms into bite-sized pieces.
Slice the onion and green onion thinly.
Heat cooking oil in a pan and stir-fry the onion and green onion.
Add the mushrooms and stir-fry.
Add the tofu and cook until golden brown.
Season with soy sauce, sugar, sesame oil, and pepper.
Place the stir-fried mixture over rice.
Finish by sprinkling sesame seeds on top.