Lime leaves: Lime leaves (or makrut, Kaffir lime leaves or Thai lime leaves) lend one of the signature flavors to Thai cooking—lemony and floral. Like other Asian ingredients, there is no real substitute, but lime zest will work in a pinch. Find the leaves fresh or frozen in Asian markets, in natural-foods stores and at importfood.com. Fresh leaves may be frozen, airtight, for up to 3 months.