Melt butter in stock pot. Add chopped onion and garlic, cook for about 5 minutes, or until soft. Add white grape juice, tomatoes, salt, pepper and basil. Cook for another 5 minutes.
Cool for about 5 minutes add cream if desired. Blend soup in batches using blender until all soup is smooth. Return to stockpot, add cream and heat just until warmed through. Serve with croutons.