More Than an Onion Understudy March 9, 2012, 4:04 pm Leeks are a key ingredient in this week's City Kitchen recipe. Though readily available, they don't necessarily end up in everybody's shopping basket. We think of them as a stand-in for onions, but they really are so much more. Large leeks are good for soups and stocks, and leeks can contribute both sweetness and depth in many dishes; medium or small leeks especially. They can be delicious served separately as a vegetable, too. Braised to accompany boiled beef, or dressed in a vinaigrette, leeks are known in France as the poor man's asparagus. When preparing leeks for any recipe, the most important thing to keep in mind is that because they are grown in sandy soil, you need to wash them carefully. I use lukewarm tap water. Chop or dice the leeks first and then swish them in a large basin. Lift them from the water with a skimmer; the sand and soil will sink to the bottom of the bowl. And remember that the tender green center of the leek grows nearly to the top. This means that if you simply chop off the top, you risk discarding a lot of perfectly good leek. Peel away the tough dark outer green leaves, but make sure to use the paler green central shoot.