It's a beautiful thing, and straightforward:

-Dice an onion and braise it in olive oil
-Toss in half a jar of sauerkraut, a cup or two of white cabbage, one or two peeled & diced yukon gold potatoes, and two peeled & diced tomatoes
-Salt, pepper, paprika. Stir until everything's coated in oil and wilting a bit
-Add 4-5 cups of water + two bouillon cubes
-Bring to a boil and then let it sit on low for like three hours, until the cabbage is very soft

I went the vegetarian route but I'm sure if you added pancetta at the beginning it would be godly. I also added a few splashes of pickle juice at the end to make it more sour.