Instructions

  1. Heat the milk over moderate heat in a medium pot.
  2. Put tomatoes, tomato paste, onions, salt and pepper, sugar, flour, butter, and celery into a food processor and grind until smooth.
  3. Pour mixture into milk and raise heat to bring soup to a boil.
  4. Reduce heat and then simmer 15 minutes.
  5. While soup cooks, make pesto, if not using storebought.
  6. Fill the food processor with watercress, loosely packed.
  7. Add hazelnuts, 1/2 of the oil and garlic cloves to the watercress in the processor.
  8. Add nutmeg, salt and pepper to the processor bowl, set lid in place and pulse grind the mixture into a thick paste.
  9. Add any remaining watercress to the processor and grind into the paste by pulsing the processor again.
  10. Transfer watercress paste to a bowl.
  11. Stir in the remaining oil and the cheese.
  12. Taste pesto sauce and adjust seasonings.
  13. Pour soup into shallow bowls and add a couple of rounded spoonfuls of pesto to each dish and stir it into the soup.