1. Heat oil and margarine in large stock pot. Add the onion and let cook for 2-3 minutes.
2. Add leek, carrots and celery and cook for about 5-8 minutes, stirring frequently to make sure not to brown. Add a little salt and pepper and 2/3 of the parsley.
3. Cook for 1 minute then add water and potatoes. Bring to boil, reduce heat and simmer for 20 minutes or until potatoes are soft.
4. Use an immersion blender to "cream" soup. Add a little more salt and pepper, to taste. Enjoy!
Source of recipe: This recipe is from my mom. She made this all of the time when I was a kid.