Clean, wash and roughly chop the spring onions and watercress. Melt butter in a pot. Sauté the spring onions and watercress (put some cress aside) briefly in it while stirring. Dust with flour and stir in. Gradually add stock and cream, bring to the boil and simmer covered for about 10 minutes. Peel carrots, leave some green, wash and cook in boiling salted water for about 10 minutes.
Cut ham slices in half lengthwise. Drain the carrots, let them drain well and wrap each slice of ham in half. Puree the soup, season with salt and pepper. Arrange in soup bowls, sprinkle with remaining cress and possibly pepper flakes. Add carrots