Cut the tofu into cubes, and chop the cabbage and mushrooms into bite-size pieces.
Heat some cooking oil in a pan, and fry the tofu until golden. Remove from the pan.
In the same pan, stir-fry the cabbage and mushrooms.
Add the tuna (drained of oil) and stir-fry together.
Return the tofu to the pan and season with salt and pepper.
Stir-fry everything together until well combined.