Boil the sauerkraut in half a litre of water, uncovered for about 15 minutes. In a second pot, add the cabbage and pour in just enough water to not quite cover; boil, uncovered, until tender, 25 to 35 minutes.
As the cabbages boil, sauté the bacon to render the fat then remove the meat and set aside. Brown the pork and beef in the bacon fat, adding lard or other cooking fat, if necessary. Keep the meat with the cooked bacon and reserve the cooking juices. If you’re using fresh mushrooms, sauté them (with garlic, if using).
In the larger of the two pots, combine the cabbage and sauerkraut and their cooking waters, cooked meats and their juices, sausage, mushrooms (dried or sautéed), prunes (if using), bay leaf and spices.
Bring the uncovered pot to the boil and keep it there for 10 minutes, then lower the heat and let simmer, still uncovered, for 1 hour (or longer, if you wish), stirring occasionally, being sure to add water if you think the pot boil may dry. It should be sour, but balance flavours to taste.