Defrost the spinach in the microwave for 2 minutes. Drain any excess liquid.
In a medium sized bowl, add the tuna, spinach, salt and black pepper. Add the egg and mix well with your hands and form into patties. Adapt the thickness and size depending on how many you want to make. I usually make them with about 2cm thickness.
In a frying pan over a medium heat, warm the oil then fry the patties on each side for around 2 minutes or until golden brown. Remove from the pan and serve hot.