1. In a large pot, heat the oil over moderately low heat. Add the onion; cook, stirring occasionally, until translucent, about 5 minutes.
2. Add the cabbage, potatoes, water, broth, bay leaf, thyme, and salt to the pot. Bring to a boil. Reduce the heat and simmer, partially covered, stirring occasionally, until the cabbage and potatoes are tender, about 20 minutes.
3. Meanwhile, put a large nonstick frying pan over moderate heat. Add the sausage and cook, stirring occasionally, until browned, 2 to 3 minutes. Remove the sausage from the pan and drain on paper towels. Just before serving, remove the bay leaf from the soup and stir in the sausage.
In a separate pan, cook three quarters of a pound of sausage links, cut into slices, and stir them into the soup instead of the smoked sausage.
Wine Recommendation: Portugal, while justly renowned for its ports and Madeiras, is also a great source of excellent values in robust, dry red wines. The earthy, spicy richness of these reds is perfect for rustic fare such as this. Ask for one at your local wine shop.