Add yellow onions and garlic to drippings in skillet; cook on medium heat 5 min. or until tender, stirring occasionally. Stir in flour; cook 1 min., stirring constantly. Add broth, cauliflower, potatoes, carrots and thyme; stir. Bring to boil; simmer on medium-low heat 20 min. or until vegetables are tender, stirring occasionally. Remove and discard thyme sprigs.