Mushrooms Green Beans and Tomato in Cream Sauce

13 oz. mushrooms,
6oz. green beans,
1/2 pt. heavy cream,
2 T. butter,
2 1/2 oz. onion,
8 ea. grape tomatoes
2 garlic cloves,
1/2 tsp. salt,
1/2 tsp. black pepper or white if you don't want to see the black pepper,
2 T. pecorino romano cheese.