Hot-and-Sour Soup with Shrimp, Napa Cabbage, and Shiitake Mushrooms

Using Thai red curry paste is an easy way to add tons of flavor and some heat to your cooking. It is available in the Asian foods section of most supermarkets; at Asian markets, it is known as gaeng pet. Kaffir lime leaves, which come from kaffir lime trees in Southeast Asia and Hawaii, have a floral-citrus aroma. The leaves are sold frozen and are sometimes available fresh at Southeast Asian markets.