Peel the potatoes and cut into chunks, add salt and boil until done. Drain and set aside.
Place the fish in a frying pan with the diced onion, garlic, parsley and pepper.
Add enough milk to almost cover and bring to a slow boil. Simmer for a few minutes, turning, until the fish is cooked and flaking apart.
Remove fish, onion and garlic from the milk to a bowl. Gently break the fish apart into flakes, using a fork.
Mash the potatoes with butter and a little of the milk from the fish.
Carefully combine the fish with the mashed potato, lemon zest and two eggs. Season with salt and pepper to taste.
Refrigerate fish mixture for about half an hour.
Drain off any excess liquid and form the mixture into 3" (7.5 cm) balls.
Dredge each ball in flour, then roll in the beaten eggs, finally rolling them in the breadcrumbs to coat.
Pat the coated fish to flatten into patties and place in an oven-proof pan that has been lightly oiled.
Lightly drizzle or spritz olive oil onto the tops of the patties.
Bake at 375°F or 190°C for about 30 - 40 minutes, until golden brown, turning once.