Instructions

1. 1
   Roast the potatoes in the oven until tender. Cool slightly.
2. 2
   Mash the potatoes, mixing in the milk, pepper, lemon juice, and eggs, if using.
3. 3
   Mix in the olives. Season with salt to taste.
4. 4
   Prepare the cod by leaving it for 24 hours in water, changing the water once or twice.
5. 5
   After the 24 hour period is up, put the cod in a pot with milk.
6. 6
   Boil the cod until slightly cooked, then season with salt and pepper. The milk will make the fish soft.
7. 7
   Slice the onions into rings, and fry in pan with garlic and lots of olive oil until slightly browned.
8. 8
   Preheat oven to 220°C (425°F).
9. 9
   Place the cod in the center of a casserole or baking dish.
10. 10
    Surround the fish with 500 g of the mashed potatoes, then top it with the fried onion.
11. 11
    Cover the onion with a thick layer of mayonnaise, and sprinkle bread crumbs all over.
12. 12
    Bake until toasted on top.
13. 13
    Serve with a green wine from the north of Portugal.