3/4 c. milk
1 can cream of mushroom soup
4 med. potatoes, sliced 1/8" thick
1 c. grated Cheddar cheese
1/2 c. onion, chopped

Combine milk and soup in a microwave 2 quarts casserole. Stir in remaining ingredients. Cover and microwave on high for 10 minutes. Stir. Microwave for another 12 minutes or until potatoes are tender.