Pasta with Mushrooms and Onions

If you are looking for a really easy side dish, this is it.  It can also be made in advance.  The whole thing uses 4 ingredients.  You can’t beat that.

1  (12 oz) pkg. alphabet pasta or any other small pasta
1 stick butter or margarine
1 envelope dry onion soup mix 

Preheat oven to 350 degrees.
Cook pasta and drain. Mix all ingredients together and put in a casserole dish. Bake  for about 20 minutes.