Leeks have a good amount of sand trapped between the layers in both the white and green parts. Be sure to soak, rinse and clean well so as not to spoil the final results.
Add olive oil, sliced leeks and ginger to a large sauce pan over medium heat. Cook for 2 to 3 minutes until the leeks begin to soften and the ginger becomes fragrant.
Peel and slice the parsnips into 1/4 inch thick disks. If the vegetables are large, cut in half lengthwise before slicing. Add the sliced parsnips to the pot and cook an additional 7 to 8 minutes. Should the pan get dry, add 2 to 3 tablespoons of the vegetable broth to keep the pan from scorching.
Add the vegetable broth and bring to a boil. Reduce to a simmer and add the white wine. Cook for 20 minutes uncovered. When done the vegetables should be soft and tender.
Place the soup in a food processor or blender and blend until smooth. (I use an immersion blender for this step.) Season with white pepper and salt to taste.
Ladle into bowls and garnish with a small dollop of yogurt (or for a more elegant presentation you can thin the yogurt and make swirls or a web pattern) and a small sprinkle of smoked paprika.