Dry Onion Leek or strands from tightly concentric, succulent layers of grooved, strap-shaped, grey-green leeks leaf bases. Dried leeks have a flavor more refined, subtler, and sweeter than the standard dried onion. The dried leeks can be used in breads, soups, stews, and casseroles. If dried leeks are unavailable, substitute a slightly lesser amount of dried onions, or dried chives.