1) In a pot, combine the stock, water and split peas.
2) Bring to a boil, partially cover and simmer for 30 minutes.
3) Add the onions, carrots, celery, soy sauce and dill.
4) Cook over medium-low heat, stirring occasionally, for 30 minutes, or until the peas and vegetables are tender.
5) Puree the mixture in a blender.
6) Reheat, the soup if necessary, before serving.
7) To serve, ladle into individual bowls.
8) Top with spoonful of the yogurt.