These are the leaves of a lime tree native to tropical Asia. The leaves are shaped like a figure eight, with two leaves held together from the tip to the base. The small fruit of the kaffir lime can also be purchased from Asian food stores. Imparting their full, fresh, citric flavor, both the aromatic leaves and the bitter rind are used in Thai cooking, primarily in chicken and fish dishes. To use, slice the kaffir lime leaves finely, which will give a stronger flavor, or crush them as you would bay leaves.
** Asian Recipes