Heat a non-stick frying pan over medium-high heat and add oil. Add onions and cook for 5 min until soft and starting to colour.
Transfer to slow cooker insert, add the tomatoes and stock. Squeeze sausage meat out of casing, breaking into 2cm pieces, and add directly to the liquid.
Cover the slow cooker and cook on high for 2 hr (low 4 hr). With the slow cooker on high, add the cabbage, beans and pasta. Stir, then cover and cook for a further 1 hr. Season to taste. Serve with crusty bread and garnish with chopped parsley.