medium leeks, white part only
flavorless cooking oil
potatoes, peeled and diced
Remove the root end of the leeks, trim the dark green tops and reserve for another use.
Slice the light part into 1/2-inch rounds, wash well and set aside on a plate.
Heat the oil in a pot, over medium heat, and add the leeks.
Cook, stirring for 5 minutes.
Add stock, water, potatoes, nutmeg, salt and pepper.
Raise heat to high, cover and bring to a boil.
Reduce heat to low and simmer, uncovered, for 30 minutes.
Remove from heat and puree the soup in batches.
Place pureed soup in a pot and reheat, covered, over low heat.
To serve, place a generous dollop of sour cream in the bottom of each soup bowl and sprinkle with chopped chives.
Transfer piping hot soup to a tureen or pitcher and pour into bowls at the table.
Refrigerate soup for up to 3 days or freeze the soup in 3-cup batches.