Sprinkle the meat with salt and pepper and place it in a large heavy kettle, fat side down. Add about 1/2 cup of water. Cook, covered, over medium heat for about 15 minutes.
Uncover the meat and continue cooking until the liquid has evaporated and the meat begins to brown. Brown on all sides.
Add the onion, about five cups of water, and continue cooking at a simmer for about another 45 minutes, uncovered.
Add the chestnuts and continue cooking. Check periodically to be sure the liquid hasn't boiled dry.
Peel the rutabagas and cut them into two-inch pieces, keeping the size as uniform as possible. Add the rutabagas, the rest of the water, and cook for about another 45 minutes, covered.
Taste for seasoning and add salt and pepper to taste. The meat, the rutabagas, and the chestnuts should all be tender.
Remove the roast to a heated serving platter. Use a slotted spoon to scoop the chestnuts and rutabagas out, and place them around the meat.
Pour the fat off of the accumulated juices in the pan. Add enough chicken stock to the pan to make approximately 1 ½ cups of liquid.
Boil vigorously in order to melt the burned on juices, and to combine the flavors. This liquid can be thickened and used as a gravy, or used "au jus" and poured over the meat and vegetables.