2 large leeks
2 pound yukon gold potatoes, cubed
5 cups vegetable broth
2 cups water
1 tablespoon unsalted butter
1 teaspoon minced fresh dill
1/4 teaspoon white pepper
1/4 cup dry white wine
1/4 cup whipping cream (optional)

1. Remove the leeks' root and tough outer; halve lengthwise.

2. Soak in 10 cups of water with 2 tablespoons of white vinegar for 30 minutes.

3. Rinse well and chop.

4. Melt butter in a large stock pot over a medium-high heat.

5. Add chopped leeks, cook till softened.

6. Add the remaining ingredients.

7. Simmer over a medium-low heat until the potatoes fall apart (about 1 hour).

8. Remove from heat.

9. Using an immersion blender, puree to desired thickness.

from HERE