Place the fish in a shallow pan with the water, coarse salt, carrot, and onion; simmer until fish easily flakes, about 8 to 10 minutes, depending on the type and thickness of the fish.
While the fish is cooking put the fresh breadcrumbs, milk, ½ the egg, salt, pepper and parsley in a small bowl.
Carefully lift the fish and carrot out of the water with a slotted spatula or strainer and place in a bowl to cool to room temperature. Discard the cooking water and onion.
Dice the carrot and add it to the breadcrumb mixture. Flake the fish with a fork, then add it to the breadcrumb mixture; add salt and pepper to taste and combine well.