Saute the onions in butter until very tender.Add the mushrooms and saute for about 2-3 more minutes.
Add the wine, simmer, and reduce by half.
Add the beef gravy and tomato puree and simmer for about 5 minutes.
Add the Maggi seasoning, salt and pepper to taste (you can also try adding your favorite herbs to this sauce).
Serve with steak or roasted turkey or chicken.