Leeks require a thorough cleaning to wash out all the sandy grit trapped between the layers.
Cut them open and submerge the layers in cold water to dislodge the dirt. Take a little extra time to wipe away dirt if necessary.
Once clean, leeks work well in plenty of dishes, imparting their wonderful oniony flavor.
Try chopping them and sautéing them in some oil or butter, and then using them to top a bagel with lox or cream cheese. Use them in soups, along with onions. They are classic in leek and potato soup, and delicious roasted.
To roast leeks, trim the roots off the leeks and trim off about 2 inches of the greens. Cut the leeks in half lengthwise, stopping just short of cutting them all the way through at the bulb, so that each one remains held together. Rinse thoroughly and dry. Set the leeks on a baking sheet and brush them liberally with olive oil. Roast them until knife-tender, about 20 minutes.
Remove the leeks from the oven and brush with balsamic vinegar. Season with sea salt and pepper to taste and serve hot or warm.