Grate the onion and mix all the sauce ingredients into the grated onion thoroughly.

Place the mixture on plastic wrap, shape it into a square about 1 1/4 inches high, and cut into cubes.

Heat vegetable oil in a frying pan, add the meat, and cook over medium heat, rolling until browned on all sides.

Once cooked, use a paper towel to remove excess oil, add the sauce made in step 1, and mix while evaporating the sake.