How to prep a leek
Leeks are underappreciated and underused. Their flavor is mellow, complex and more subtle than other members of the onion family, and they go tender and silky when cooked.
They’re known for their role in potato and cream-based soups (like vichyssoise) and in winter stews. They’re delicious raw and sliced thin in salads, stir-fried with beef (or anything, for that matter), simmered in water and served hot or cold with a vinaigrette, braised whole in wine or stock, or brought in anywhere you’d use an onion.
No matter what form you want your leek to take, you’ll need to isolate and clean the usable white and light green parts.
Start by cutting off and discarding the root from the leek’s bottom end. If you’re planning to cook the leeks whole or as halves, try to leave enough of the fibrous white part above the roots to hold the halves together. If you’re planning to slice the leeks, you don’t need to be so exact here.
Next, chop off the tough top part of the leek between the light green and dark green parts (let's call it medium green). Either discard the dark green part, or rinse it well and use it to flavor a stock, broth, or poaching liquid.
Next, cut the leek in half lengthwise. If you’d like insurance that the leek will stay together for washing, leave the root end intact.
Now it’s time to get rid of the sand and soil that wedges between the leek’s layers. Be thorough here — a gritty bite is a deal-breaker. Rinse the leek under cold running water, making sure to spread the layers apart with your fingers to remove any hidden sand or soil.
Alernatley, If this is too much, you can take the short cut and slice them sand and all, and afterwards rinse them well in a colander submerged in a bowl of cold water and pat them dry.
Now all you have to do is finish cutting the leek in half lengthwise (if you haven’t already), and choose your slice - crosswise for little half moons, or lenghtwise for matchstick sized pieces. Remember the longer the cooking time, the thicker the slice should be to hold up well.