Scrub and wash potatoes. Lay them in an even layer in the microwave and cook for 10 minutes.
Remove from the microwave and allow to cool. While they are cooling, in a medium bowl, mix together onion powder, cream of mushroom soup, and milk (I used one of the empty soup cans to measure my milk).
When the potatoes have cooled, peel and slice them into 1/8 inch rounds.
In the bottom of the baking dish, pour 1/3 of the mushroom soup mixture.
Sprinkle ½ cups of cheese over the soup and then layer the potatoes on top.
Spread another third of the soup mixture of the top along with another half cup of cheese, then add a second layer of potatoes.
Spread the remainder soup mixture of the top and sprinkle the rest of the cheese on top.
Bake at 400 for 40-45 minutes or until the potatoes are tender.
Garnish with fresh chopped green onions and serve.