The leek has been highly esteemed in many food cultures since ancient times. Like all alliums, leeks have great health promoting properties.
Selection and Storage:
Leeks should feel firm and heavy for their size and be straight, bearing dark green leaves. There should be no evidence of yellowing or withering. Store leeks with leaves attached, in the refrigerator, loosely wrapped in plastic, for a week.
The coarse green leek tops are discarded and the white part only is used for cooking, although the green part can be utilized, well washed, in stock-making. The trickiest aspect of preparing leeks for cooking is the removal of all the first that hides between the layers. If you plan to use keeps sliced, simple slice and wash in plenty of water. If planning of using leeks whole, make a deep, crosswise slit through the leafy end of the leek, then soak in a bowl of water, shaking them well to dislodge any dirt.
Never simply boil leeks or the result will be soggy and tasteless. Leeks are delicious braised whole, steamed or pureed into soups.
Information from: The Produce Guide by Leanne Kitchen.