Leeks are a type of vegetable that are often used in recipes. The edible part of the leek is the white and light green part of the plant. The dark green leaves are generally too tough to enjoy, but they can be used to make homemade stock or soup. To prepare a leek, first cut off the stringy roots and dark green leaves. Then, cut the white and light green part of the leek in half lengthwise and lay the flat side down on the cutting board. Cut into 1/4 to 1/2 inch half slices. Finally, clean the leeks by placing the cut pieces in a bowl of water and swishing them around to loosen any dirt or sand that is stuck in the leeks.