Heat oil in a large saucepan or pot. Add leek and garlic, cooking for 5 minutes until leek is tender. Add stock, sweet potato and superblend mix. Bring to the boil, reduce heat and simmer for 10 minutes.
Stir in beans, tomatoes and balsamic. Season well. Cook a further 5 minutes. Serve soup with some freshly torn basil leaves stirred through.