In a bowl, flake the mackerel from the can and mix with chopped green onion to create the mackerel filling.

Pat the fried tofu with a paper towel to remove excess oil, cut each piece in half, and open them. Stuff each piece with an equal portion of the mackerel filling.

Heat salad oil in a frying pan over medium heat. Place the stuffed tofu pockets in the pan and cook until both sides are golden brown. Add pizza cheese on top, cover with a lid, and steam on low heat until the cheese melts.