In a large saucepan coated with PAM, cook the carrots, celery, and onion in butter for 3 minutes. Add broccoli; cook 3 minutes longer. Stir in 2-3/4 cups milk, salt, thyme, and pepper. Bring to boil. Reduce heat; Cover and simmer for 5-10 minutes or until vegetables are tender. Combine the flour and remaining milk until smooth; gradually stir into the soup. Bring to a boil; cook 2 minutes longer or until thickened.