In a frying pan, heat the vegetable oil with 1 tablespoon of butter and fry the onion for 5 minutes, but do not let it fry. Add the seasoning and cook for another 1 minute.
Lightly mash the tuna with a fork, if there is too much liquid in it, then drain part of it.
Add the tuna to the pan, stir and cook for a couple of minutes. Switch.
Chop the garlic and parsley.
Grate the cheese on a fine grater.
Beat the eggs, add milk, cheese, garlic and parsley again.
Peel the potatoes, grate them on a coarse grater and squeeze out excess moisture.
Grease the mold with oil, put a mixture of onions, dressing and tuna, add potatoes. Pepper to taste, mix.
Pour in the egg-cheese mixture, mix lightly. Crumble the pieces of butter on top and bake in the oven at 190 ° C for 40 minutes.