Heat oil in a deep pot. Add leeks, garlic, celery, carrot & parsnip. Sauté at low to medium heat for 7 minutes or until vegetables start to become soft.
Add potatoes, chicken stock, pepper, thyme, & salt to taste. Bring to a boil then reduce heat. Cover & simmer for 20 - 25 minutes or until vegetables are tender. Puree in a blender (or use a hand blender directly in pot.) Add parsley, then salt & pepper to taste, stir and serve.
If using frozen celery, about 1 1/2 cup chopped. If using frozen carrot, about 1/2 cup chopped. Use chicken or vegetable stock. If using chicken stock that you have made yourself, skim the fat off first. If you understand the Weight Watchers PointsPlus® system, 1 cup of this soup is only 1/2 point.