Heat 2 tbsp. oil in a large nonstick frying pan over medium heat. Add onion and caraway seeds; cook until onion softens, 10 to 15 minutes. Add sauerkraut, lower heat to medium-low, and cook, covered, stirring occasionally, 10 minutes. Scoop into a bowl; cover. Wipe pan clean.
Put potatoes and bay leaves in a medium pot and add just enough water to cover, plus salt to taste. Bring to a boil, then simmer until potatoes are tender, 15 to 20 minutes. Drain potatoes (reserve 1/2 cup of water). Return to pot. Stir in butter, cooking water, and watercress. Set aside, covered.
Pour 1 tsp. oil into pan and cook sausages over medium heat, covered, until cooked through, 10 to 20 minutes. Pour in wine and cook, turning sausages, until wine evaporates. Serve with kraut and potatoes.
Note: Nutritional analysis is per serving.