Discard the green tops of the leeks and split the leeks lengthwise.

Wash in cold running water to remove all sand. Drain and finely chop.

Peel and slice the potatoes.

Melt the butter in a large pot.

Add the leeks and sauté over moderate heat, until wilted.

Add the curry powder and cook for 1 minute.

Add the chicken stock and potatoes.

Bring to a boil, reduce the heat to low, and simmer for

45 minutes to 1 hour, until the potatoes are tender.

Puree the mixture in a food processor. Cover and chill.

When ready to serve, whisk in the buttermilk, adjust the seasoning.

Serve in chilled bowls, with a sprinkling of the chopped chives and a grind of black pepper.