1. In a large nonstick pot, heat 2 tbsp olive oil; add 1 lb sliced leeks and 1 chopped onion. Cook on medium heat for 10 minutes; stir occasionally. Add 2 lbs potatoes, peeled and cut into 1-inch pieces. Stir in 7 cups water, 2 chicken bouillon cubes, 3/4 tsp salt, 1/4 tsp black pepper and 1/8 tsp ground nutmeg. Simmer, covered, over medium heat for 40 minutes, stirring occasionally. Puree in batches. Blend 1 cup soup with 1/2 cup sour cream, then add back to remaining soup. Garnish with chives.