Preheat oven to 350 degrees
Place tatertots on baking sheet, place in oven for 10 minutes
In large pan melt butter and sauté onion and mushrooms, salt and pepper
Add Mushroom soup and milk, heat until well mixed
In a second frying pan, crumble hamburger, salt and pepper, cook till brown
Place green beans in bottom of baking dish
Add cooked hamburger to baking dish
Add Mushroom soup / onion mixture to baking dish, covering hamburger evenly
Add shredded cheddar cheese on top of mushroom soup mix
Place tatertots evenly on top of cheddar cheese
Cover with tin foil and Bake for 40 minutes
Remove foil, let stand 5-10 minutes
