Step 1Trim any yellow or green spots from the chicken livers. Soak them in one-third cup of the milk with the salt in the refrigerator for at least 3 hours. Drain, rinse and pat dry.
Step 2In a large saucepan of boiling salted water, blanch the Swiss chard leaves (save the stalks for another use) for 1 minute. Drain, rinse under cold running water until the water runs clear, and squeeze dry. Finely chop the Swiss chard.
Step 3In a food processor, combine the chicken livers, hearts, gizzards, ham and pancetta. Pulse until coarsely chopped. Add the onion, shallot and the flour and process until well blended.
Step 4In a mixing bowl, soak the bread in the remaining one-third cup milk for a few minutes to soften. Press out and discard the excess moisture; leave the bread in the bowl. Add the egg and mix with a fork until they are light and well combined. Mash in the chicken liver mixture, then add the Swiss chard, chives and parsley. Season with the salt, pepper, nutmeg and sugar. Cover and refrigerate the stuffing for at least 2 hours or overnight to mellow and firm up. Makes 2 to 3 cups.
Step 1Up to a day ahead, make the stuffing.
Step 2About 2 hours before serving, blanch the cabbage leaves for 4 to 5 minutes in boiling salted water. Rinse under cold running water and drain. If the ribs are very thick, shave them off with a knife.
Step 3Enclose each chicken breast in one-half cup of the stuffing [by laying 2 blanched cabbage leaves overlapping on a work surface, spreading one-fourth cup stuffing in the middle of the leaves, placing a chicken breast on the stuffing and then spreading one-fourth cup stuffing to cover the breast]. Wrap each breast in 2 cabbage leaves, rib sides out, and tie securely with string [by rolling the bottom of the leaves over the chicken and folding over again to enclose the breast in cabbage, then tying in 4 places with kitchen twine]. (If desired, wrap each cabbage roll in a 12-inch square of cheesecloth and tie with string.)
Step 4About 1 hour before serving, bring the stock to a boil in a 5-quart casserole. Add the leeks, carrots and turnips and simmer until tender, about 20 minutes. Remove the vegetables and set aside.
Step 5Add the cabbage rolls to the simmering broth and poach them over low heat for 25 minutes. Remove the cabbage rolls to a work surface and let them rest for 5 minutes. Remove the strings (and cheesecloth, if used) from the cabbage rolls.
Step 6Meanwhile, reheat the vegetables in the stock; drain. Cut each cabbage roll into 4 slices slightly on the diagonal. Arrange the slices cut side up, on warmed plates. Sprinkle the chicken with fleur de sel. Surround each serving with assorted vegetables; moisten with a few tablespoons of the cooking liquid. Drizzle a little walnut oil over the chicken and vegetables and serve at once.