Soak the salt cod for 12 hours, changing the water frequently. Then put it in a pan, cover with fresh cold water, and bring slowly to a boil. Take off the heat and leave it in the water to swell and poach for 15 minutes.
Boil the potatoes in their skins, then drain and peel. Mash them very smooth.
Drain the fish thoroughly. Skin, bone, and flake it. Add it to the mashed potatoes