Vegetarian shepherd`s pie

1 1/2 cups hot water
1/2 cup milk
2 tablespoons butter or margarine
1/2 package Betty CrockerR four cheese mashed potatoes
3 cups frozen vegetables, any variety, thawed and drained
1 can (11 ounces) condensed Cheddar cheese or cream of mushroom soup
1 can (4 ounces) sliced mushrooms, drained
1 can (2.8 ounces) French-fried onions
Total time: 45 min

1. Heat oven to 350?F. Heat hot water, milk and butter to a rapid boil in 2-quart saucepan. Remove from heat. Stir in 1 pouch Potatoes and 1 pouch Seasoning just until moistened. Let stand about 1 minute or until liquid is absorbed. Whip with fork until smooth; set aside.
2. Stir remaining ingredients except onions in large bowl. Pour vegetable mixture into ungreased 1 1/2-quart casserole; sprinkle with half of the onions. Spread potatoes over onions.
3. Bake uncovered 25 minutes; sprinkle with remaining onions. Bake 3 to 5 minutes longer or until mixture is hot and onions are brown.