Heat oven to 375. In skillet over medium-high heat, cook onions in 1 Tbs. corn oil 3 minutes.
In bowl, combine bread and milk. Let sit 3 minutes. Stir in onions and next 6 ingredients. On broiler pan, shape meat mixture into 10" x 7" loaf. Bake 1 hour, or until thermometer inserted in meat reads 160. Transfer meat to platter; reserve drippings.
In skillet over medium-high heat, cook mushrooms in remaining corn oil 1 minute. Add flour; cook 1 minute. Add heavy cream, beef broth and reserved drippings. Increase heat to high and bring to a boil. Reduce heat to medium and let simmer 3 minutes. Serve gravy with meat loaf.