Remove the king prawns from their shells except for the tail end, wash and pat dry. Clean, wash and cut the leek diagonally into fine slices. Heat 20 g fat in a pot and steam the leek for 3-5 minutes. Season with salt and pepper. Take out something to garnish and put aside.
Add chicken stock to the leek and simmer for about 5 minutes. In the meantime, heat the remaining fat in a pan and fry the prawns in it for 3-5 minutes. Season with salt and pepper. Puree the soup with a hand blender and season to taste again. Arrange soup, remaining leek and king prawns on plates and serve sprinkled with pepper