Source: "From Asparagus to Zucchini: A Guide to Farm-Fresh, Seasonal Produce."
1/2 teaspoon salt
1 pound potatoes, peeled & cubed (about 2 cups)
1 pound leeks, cleaned (clean by cutting in half lengthwise and washing them thoroughly under running water), & thinly sliced
1/4 cup chopped fresh parsley (optional)
1 tablespoon butter
Bring 8 cups water to a boil in a stock pot. Add salt, potatoes, and leeks; cover and reduce heat. Cook until potatoes are soft—about 30 minutes. Set aside to cool slightly. Transfer to a food processor or blender and puree. Do not over-blend or potatoes will become sticky. Return to pot, stir in parsley and butter, and reheat.