This paste is a study of contrasts. The searingly hot Thai chilies are balanced by the sweetness of the tamarind and brown sugar and the saltiness of the dried shrimp and fish sauce.
2 tablespoons vegetable oil
1 medium to large onion, minced
2 serrano chilies, seeded and chopped
1 (½-inch) piece ginger, peeled and chopped
1 teaspoon ground coriander
4 tablespoons fermented yellow beans (fermented soy beans)
2 tablespoons lime juice
2 tablespoons water