Cut the bok choy into bite-sized pieces.
Dice the tofu and pat dry with a paper towel.
Heat cooking oil in a pan and fry the tofu until golden brown.
Push the tofu to one side and add the tuna, stir-frying lightly.
Add the bok choy and season with salt and pepper.
Stir-fry all ingredients together for a bit longer.
Serve the stir-fried mixture over rice.