In a Dutch oven, cook onion and garlic in butter until the onion is tender.
Stir in soup and tomato juice until combined. Add milk, basil, oregano, and black pepper. Bring to a simmer and cook, uncovered, for 10 minutes.
Cook tortellini according to package directions, except cook carrots with tortellini. Drain off the water.
Add the pasta and carrots to the tomato soup. Stir in chicken. Heat through. Garnish with sprigs of oregano, if you like. Makes 6 servings.