In deep non stick frying pan, heat oil over medium high heat. Add sausage and brown on all sides, about 5 minutes. Add cabbage, onion, garlic, and caraway seeds; cook, stirring, until cabbage has wilted slightly, about 3 minutes.
In bowl, whisk together stock, vinegar and mustard. Add to frying pan along with barley; stir. Bring to simmer; cover and cook, stirring occasionally and adding more water if too dry, for 40 minutes or until barley is tender.