In a large stock pot melt the butter and soften the onion and garlic. Add the mushrooms to sauté.
Drain and rinse the sauerkraut. Shred the white cabbage.
Add these to the pot along with the stock and chopped tomatoes. Bring to a simmer.
Cut the sausage and meat into 1/2 inch/12mm chunks.
In a separate pan, brown the pork belly and transfer it to the pot.
Repeat this step for the sausage and other meats.
Pour a splash of red wine into the browning pan to deglaze. Use a spoon or spatula to lift any of the meat juices and coating. Transfer to the big pot.
Season with paprika, salt and pepper.
Add a little more water to the pot if necessary, but not too much. It doesn't want to completely swamp the ingredients, Bigos is typically a fairly 'dry' stew.
Cook on a low heat and simmer for 2 hours, or longer. I find a 4 hour simmer gives a depth of flavour.
Eat immediately or (better) leave to stand for at least 24 hours, reheat and enjoy.
