Crock pot Hamburger Casserole

I got this recipe off recipezaar and changed it a little. It turned out really tasty, but not really like a casserole.

4 medium potatoes
1 lb. hamburger
1 can cream of mushroom or celery soup
1/2 soup cap milk
1 small onion
dried rosemary
salt
pepper

Dice onion, add to pan and brown hamburger, drain fat. Slice potatoes into 1/4 inch rounds (skin off or on). Mix soup and milk until smooth. Spray crock pot. Layer in potatoes and hamburger. On each layer of potatoes sprinkle generously with salt pepper and rosemary. On top of layers pour soup mixture and season.
Cook on high for 2.5-3 hours, or low for about 6.