Combine cauliflower, potatoes, carrots, and onion flakes in a pot. Add enough water to cover, then stir in bouillon cube. Bring to a simmer and cook until cauliflower is tender, about 10 minutes.

Transfer vegetable mixture and about 1 cup cooking liquid to a slow cooker. Stir in condensed soup, milk, cream cheese, and bacon bits. Cook on Low for 2 1/2 hours, stirring occasionally.

Stir parsley into soup and continue cooking until vegetables are tender and flavors blend, 30 minutes to 1 1/2 hours.

Ladle into bowls and top with shredded cheese.