Place the turnips in a 2-gallon ceramic jar. In a mixing bowl, stir together the water, vinegar, sugar, salt and crushed grapes and pour over turnips. Cover and refrigerate for 48 hours.
In a 12 to 14-inch sauté pan, heat the olive oil until smoking over medium heat. Add onions and garlic and cook until softened, about 8 minutes. Add flour and caraway and stir through. Drain turnips and add to pan. Cook until very soft, careful not to break the turnips, about 1 hour. Transfer brovada to a bowl, cover tightly and set aside.
In a 14 inch sauté pan, heat olive oil until smoking, add and onions and speck and sweat until onions are translucent. Add cabbage and cook until tender, about 20 minutes to half hour. Season with salt and freshly ground black pepper to taste. Place cabbage in a bowl, tightly covered and set aside.
Separate the legs and breasts from the duck carcasses. Pull off the loose fat from the duck pieces and carcasses and set it aside. (Save the carcasses for stock).
In a small bowl, combine the red pepper flakes and 1 tablespoon each of salt and pepper. Rub the legs all over with this mixture. Wrap the legs individually in plastic, and refrigerate them, the breasts, and the reserved duck fat overnight.
In a small saucepan, combine the reserved duck fat and ¼ cup water and cook over low heat until the water has evaporated and the fat is liquefied, about 1 hour. Preheat the oven to 325°F. Place the duck legs in a shallow, non-reactive casserole and cover with the hot fat. Cover and bake for 2 hours. Remove from the oven and allow to cool. Keep the oven on (the legs may be stored in the refrigerator, covered in the fat, for up to 4 weeks.
Remove the legs from the cooled fat and wipe off the excess fat with a paper towel. Season the breasts and legs well with salt and pepper. With a sharp paring knife, score the breasts on the skin side with an X, making sure to penetrate the duck's skin and fat but not the flesh.
In a 12 to 14 inch ovenproof sauté pan, heat 1 tablespoon of the olive oil over high heat until smoking. Add the legs and sauté them, skin side down, until the skin is crispy. Remove the pan from the heat and place it in the oven to heat through, for about 5 minutes.
In a second sauté pan of equal size, add 1 tablespoon of the olive oil. Add the seasoned breasts, skin side down and sear them over low heat for about 20 minutes, until crispy, draining the excess fat from the pan when necessary. Turn the breasts and cook on the flesh side until they are medium rare, or approximately 130°F on a meat thermometer. Transfer the beasts to a cutting board and allow them to rest for 5 minutes, and then slice them on a bias.