Wash, peel, cut into cubes and cook the potatoes with 1 teaspoon of salt over medium-high heat in a pan filled with enough water to cover the potatoes (approx. 20 minutes) or until the potatoes are tender. Drain and let cool slightly for about 5 minutes.
Mash potatoes well with a fork.
De-salt the cod fillets-- Put the cod in a bowl and fill with enough water to cover the fillets. Refrigerate for 24 hours, changing the water about 5 or 6 times. Drain the cod before you start to cook it.
Then place the fillets in a pan with enough water to cover them and bring to a boil over medium heat. When boiling has begun, reduce heat to low and simmer uncovered for about 5-7 minutes. Drain and let cool. Flake the cod with your hands and add to the mashed potatoes.
Add the green onions, cilantro or parsley, onion, 1/2 teaspoon of salt, a generous pinch of ground white pepper, and pinch of both nutmeg and cayenne pepper. Stir everything well to form a homogeneous mixture.
Separate the whites from the yolks of 2 eggs. Add the egg yolks to the potato mixture. Place the egg whites in a clean, dry bowl and beat well with an electric mixer on medium-high speed for about 2 minutes or until firm peaks form.
Using a plastic spatula, fold the beaten egg whites into the potato mixture until completely incorporated. This will give the cakes a more delicate, airy texture.
In a shallow bowl, beat 1 whole egg and set aside. Pour the breadcrumbs onto a baking sheet and set aside.
Using a tablespoon, remove a spoonful of potato mixture and roll to make balls about the size of a walnut with shell. Repeat the process until the mixture is used up.
For breading the cod cakes, roll 1 to 4 balls at a time in the beaten egg and lift out with the help of both a spoon and fork in order to drain off excess egg. Then roll the balls well in breadcrumbs. Repeat this process with all the cod cakes.
For frying the cod cakes, heat the oil to 350° F (180 ° C) in a deep fryer (it is important that the oil reaches this temperature first before starting to fry, or else the cakes will turn out oily). Fry about 6 cod cakes at a time, for 1 to 2 minutes or until golden brown, turning at least once to evenly brown the sides.
Remove cod cakes with a slotted spoon and place on a baking sheet lined with paper towels in order to remove the excess fat. Store in a preheated oven at 190 ° F (about 90 ° C) for up to 15 minutes to keep the cod cakes warm. Serve cod cakes with lemon wedges or rosé sauce (recipe below).
To prepare the rosé sauce: Mix all the ingredients together until the mixture is homogenous. Place in a ramekin and serve accompanying the cod cakes.