Vichyssoise

Trim the leeks: remove the roots and cut where the white turns to green. Halve the white segments lengthwise.

Submerge the halves in water and flip through the layers to wash out grit, then pat dry.

Slice the leeks very thin; they are tough and fibrous if not pureed.

Peel the russets and chop into half-inch pieces. Keep them covered in cold water to wash off excess starch and prevent oxidation.

Melt the butter in a wide, high-walled skillet. Wait for the foaming to subside, then add the sliced leeks.

Saute over medium heat for three to five minutes, until sweated and beginning to soften.

Deglaze with the vegetable stock, scraping up the browned bits.

Bring to a simmer, add the potatoes and cook with the stock and leeks about 15 minutes, until completely soft and easily pierced.

Transfer to a tall, narrow, heatproof container and puree until entirely smooth. Season to taste with kosher salt.

Whisk in the heavy cream and taste again for seasoning.

Cover tightly and refrigerate at least four hours, until completely cold; it can also be served hot.

Pour into a soup bowl and garnish with more heavy cream, chives and freshly ground black pepper.