Dried salted cod:soak in refrigerator 24hrs in several changes of colc water. (Keep bowl covered with water). Drain, rinse and drain well again. (Skip above steps fro frozen cod). Place in a small saucepan, cover with water and bring to a simmer over moderate heat. Simmer for about 15 to 30 min until tender. Meanwhile, boile potatoes aobut 20 min until soft. Drain, return to pan to low heat, and shake well to drive off excess moisture. When cod is tender, drain and flake off with a fork, remove any bones and bit of skin, mince fine and reserve.
In a small skillet over moderate heat, saute the onion and garlic in the olive oil about 5 min until limp, mix in the parsley and set off the heat. Mash potatoes, mix in the reserved minced cod, onion mixture, egg yolk, cayenne pepper and black pepper. Wisk the egg wite to soft peaks, then fold into the cod mixture, cover, and refgrigerate until ready to shape the balls.
Place shortening in a deep-fat fryer, shape the cod mixture into 1 - 2 inch balls, then, as soon as the fat reaches 370F, bry in batches, until golden brown. Lift with slotted spoon to several layers of paper towling to drain. Set uncovered in a very slow oven (250F) to keep warm while frying the balance.