- 1 pound (about 26) medium shrimp (preferably with heads)
- 4 stalks fresh lemongrass, outer leaves discarded and root ends trimmed
- 6 cups water
- 1/4 cup finely chopped well-washed coriander roots and/or stems
- 1/2 teaspoon salt, or to taste
- 1/2 teaspoon freshly ground black pepper
- a 1-inch cube peeled fresh gingerroot, cut into fine julienne strips
- 1/4 cup Asian fish sauce (preferably naam pla)
- 1/4 cup fresh lime juice
- 1 small fresh red or green Thai chili or serrano chili, or to taste, seeded and sliced very thin (wear rubber gloves)
- fresh coriander leaves, thinly sliced kaffir lime leaves, and small fresh red Thai chilies for garnish if desired
- Rinse shrimp well and shell, reserving shell and heads
- Cut 3 lemongrass stalks into 1-inch sections and crush lightly with flat side of a heavy knife. In a saucepan combine crushed lemongrass with reserved shrimp shells and heads, water, coriander roots, salt, and pepper and simmer, uncovered, 20 minutes. Strain broth through a fine sieve into another saucepan.
- Thinly slice lower 6 inches of remaining lemongrass stalk, discarding remainder of stalk, and combine with broth and gingerroot. Simmer broth 5 minutes. Add shrimp and simmer 1 minute, or until shrimp are just firm to touch. Stir in fish sauce, lime juice, and sliced chili.
- Serve soup warm or at room temperature, garnished with coriander leaves, lime leaves, and chilies.