Wash the mushrooms if necessary and trim. Quarter them if large. In a sauté pan or shallow saucepan heat the oil, add the onions and sauté for 2-3 minutes until lightly browned. Add the rest of the ingredients (except the mushrooms) and bring to a boil.
Add the mushrooms, pushing them under the liquid. Boil over a high heat for 15-20 minutes until the mushrooms