Leeks grow best in sand soil and the broad, flat leaves of a leek wrap around each other, making the perfect place for sand to hide. The easiest way to remove the sand is to cut the leek lengthwise, almost to the root end. Hold the leek under cool running water while fanning the leaves, so the water can wash out the sand.
Leeks are very tasty but do take a few more minutes to clean. To save time, use a chopped large onion instead of the leeks. Or use a chopped medium onion and, for a little color, 1/2 cup sliced green onions.
This is really an all-season soup. Serve it warm on a chilly evening, and sprinkle each serving with crumbled cooked bacon to added a hearty smoke flavor. Or in the summer, chill it in the refrigerator, and you'll have a delicious, refreshing chilled soup ready to enjoy on the deck.