With a paring knife, core the cabbage. Bring a large pot of water to boil, add the vinegar, and place the cabbage in the pot, weighted with a heavy heat-proof plate to keep it submerged.

Cook until the leaves soften, about 12 minutes, remove the cabbage, and cool under running water. Carefully remove 16 whole leaves from the cabbage, saving the remainder for other uses, and set them aside to drain on paper towels. In a saucepan, sauté ½ cup of the onion in 3 tablespoons of the olive oil until translucent. Stir in the rice, add 1 cup of the chicken stock, and bring to a simmer. Cover and cook over low heat 7 minutes. Set aside to cool.

In a large heavy casserole (preferably enameled cast iron), sauté the remaining onion in the remaining olive oil until translucent. Crush the tomatoes and add to the casserole with all liquid from the can. Add ½ teaspoon of the salt ¼ teaspoon of the pepper, and the remaining chicken stock, and simmer gently while you prepare the stuffing.

In a mixing bowl, combine the ground meats, egg, bread crumbs, reserved rice, parsley, and the remaining salt and pepper, mixing well. Divide the mixture into sixteen equal portions and roll each into a sausage like cylinder about 2 ½ inches long. Working with one reserved cabbage leaf at a time, place a cylinder of stuffing perpendicular to the stem. Roll the leaf around the stuffing, forming a snug fit, and tuck in both ends of the leaf to enclose the stuffing completely. Repeat with the remaining cabbage leaves and stuffing. Arrange the cabbage rolls side by side in two layers in the casserole containing the tomato sauce and return to a simmer. Gently lift cabbage rolls from time to time to prevent them from sticking to the bottom of the pan and scorching. Reduce the heat to low and simmer gently 1 ½ hours. Cover partially during the last 30 minutes.

To serve, spoon the tomato sauce over the cabbage rolls.