Place the prosciutto in a heavy-based non-stick frying pan over medium heat and cook for 15 minutes or until crisp. Drain on paper towel.
To make the braised cabbage, heat the oil and butter in a large heavy-based saucepan over medium heat. Add the onion and cook for 5–10 minutes or until soft. Add the cabbage and reduce the heat to low. Cook, covered, stirring occasionally, for 35 minu