Brown ground beef and onion over medium heat until no pink remains. Drain any fat.
In a bowl mix together soup, milk, garlic powder, dry mustard and salt and pepper. Set aside
Place half of the Tater Tots into a greased 4qt slow cooker.
Layer beef, mixed vegetables, remaining tater tots and finally cheese.
Pour sauce over top, cover and cook on high 3-4 hours or on low 7 hours or until heated through.
Source:
spendwithpennies.com