Coconut milk, often added to curries, stews, and stir-fries, tones down the heat with its creamy sweetness. Palm sugar, made from the sap of various palm trees, comes packaged in plastic jars or as round cakes. It has a caramel flavor that enhances the salty and sour flavors of a dish. If you can't find palm sugar, substitute light brown or granulated white sugar, increasing the amount called for by about 20 percent. Limes, kaffir lime leaves, or lemongrass add a fragrant, citrusy note.
Acidic ingredients add vibrancy.
Lemongrass and kaffir lime leaves give a dish a refreshing, lingering lift. Lemongrass, the most popular herb used in Thailand, is a tall, scallion-like stalk that has a subtle lemony and citrusy flavor and fragrance. Before using, peel away the tough outer layers and crush or chop the stalk to release its flavor. Kaffir lime leaves impart a most intense floral and citrus flavor and are almost required in Thai curries. Lime zest, while not the same, will give the dish a similar refreshing citrusy flavor.