1/4 cup vegetable oil
1 large shallot, thinly sliced and separated into rings
1/4 cup tamarind pulp (from a pliable block)
1/2 cup boiling-hot water
2 tablespoons sugar
1 tablespoon soy sauce
1 tablespoon Asian fish sauce
3 tablespoons fresh lime juice
2 firm-ripe California avocados
1 tablespoon minced peeled fresh ginger
1 garlic clove, minced
2 (1 1/2- to 2-inch-long) fresh Thai chiles or 1 serrano, stemmed and minced (including seeds)
1/4 teaspoon salt
1 lb large shrimp in shell (21 to 25 per lb), peeled, leaving tail and first
segment of shell intact, and deveined
1/3 cup roasted salted peanuts, chopped
Accompaniment: jasmine rice
Garnish: fresh cilantro sprigs

Fry shallot and make tamarind sauce:
Heat oil in a 1-quart heavy saucepan over moderate heat until hot but not smoking, then fry shallot, stirring, until golden brown, about 2 minutes.
Transfer with a slotted spoon to paper towels to drain (shallots will crisp as they cool). Reserve oil.
Soak tamarind pulp in boiling-hot water in a small bowl until softened, about 5 minutes. Force pulp through a sieve into a bowl, discarding solids. Add sugar, soy sauce, fish sauce, and 1 1/2 tablespoons lime juice and stir until sugar is dissolved.

Cut avocados and cook shrimp:
Halve, pit, and peel avocados. Cut into 1 1/2-inch chunks and toss with remaining 1 1/2 tablespoons lime juice in a bowl.

Transfer reserved oil to a 12-inch heavy skillet and heat over moderately high heat until hot but not smoking, then saut� ginger, garlic, chiles, and salt, stirring constantly, until fragrant, about 30 seconds. Add shrimp and saut�, turning over once, 2 minutes total. Stir in tamarind mixture and simmer until shrimp are just cooked through, about 2 minutes more.

Spoon shrimp and avocado over rice, then sprinkle with peanuts and fried shallot.

Makes 4 servings.