Leeks, sweet, moderately flavored members of the onion family, are long and cylindrical with a pale white root end and dark green leaves. Select firm, unblemished leeks, small to medium in size. Grown in sandy soil, leeks tend to collect grit between their tightly layered leaves; clean thoroughly before use.
To trim, clean, and slice or chop leeks:
With a knife, remove the leaf ends or whole leaves. Trim off the roots. Starting 1 inch (2.5 cm) from the root end, slit the leek lengthwise. Fill a basin or sink with cold water and swish the leeks in the water. Repeat if necessary to remove all dirt. Cut crosswise to slice. Chop into smaller pieces if desired.For other onion varieties, see boiling, green, Maui, pearl, red, Vidalia, Walla Walla, white, and yellow onions and shallots.