Cook ground beef on stovetop until no longer pink, then drain and put into slow cooker with diced onion, condensed soup, salts and diced potatoes. Stir together.
Set to high for 3 hours. Stir and pour in broth now, stir again.
Pour in uncooked elbow macaroni noodles and submerge into liquid on top. Cover crockpot again and cook an additional 30 minutes on high.
Lift lid, stir. Add 2 c cheese and sour cream. Mix together well, then sprinkle remaining 1/2 c cheese on very top. Cover and cook for the last 20 minutes.