Wash, peel and halve the potatoes and cook them in salted water. Wash and clean the leek, cut into slices and blanch in salted water for about 4 minutes, then drain. Season with pepper.
Fry the fish fingers in the oven at 200 ° C according to the package instructions.
Drain the potatoes, add milk and butter and mash the potatoes to a puree. Season to taste with salt.
First put the mashed potatoes in a baking dish, spread the leek on top and finally spread the fish fingers on top. Sprinkle with the cheese and bake in the oven preheated to 180 ° C for about 15 minutes.