Beef with Rosemary Mushroom Sauce

The picture isn't very appetizing, but this sauce is AMAZING! So good over mashed potatoes as well.
Recipe from The Best of Cooking Light cookbook
Serves 4

1 8oz package presliced mushrooms
1 cup red cooking wine
1 lb boneless top sirloin steak
1 cup chopped green onions
1/4 cup chopped fresh parsley
1 1/2 teaspoons chopped fresh or 1/2 teaspoon dried rosemary
1 teaspoon balsamic vinegar
4 garlic cloves, minced
1 10 1/2oz can beef consomme
1 8oz can tomato sauce
2 tablespoons butter

Combine mushrooms, wine, and steak in a large zip-top plastic bag. Marinate in fridge for 30 minutes, turning occasionally. Remove steak from bag, reserving marinade. Melt 2 tablespoons butter (cookbook called for the skillet to be sprayed with cooking spray instead of using butter but I chose to live dangerously!) in a large nonstick skillet over medium-high heat. Add steak and cook until desired degree of doneness. Remove from pan.
Combine onions, 2 tablespoons parsley, rosemary, and remaining ingredients. Add onion mixture and reserved marinade to pan. Bring to a boil, cook until reduced to 2 cups (about 15 minutes), stirring frequently.
Cut beef diagonally across grain into thin slices. Place beef on plates and cover with mushroom sauce. Sprinkle with parsley.