3/4 lb large shrimp in shells (18 to 20), peeled and deveined
1 tablespoon chopped fresh tarragon
2 teaspoons Dijon mustard
1/4 teaspoon black pepper
3 tablespoons olive oil
2 firm-ripe California avocados (preferably Hass)
1 lb Belgian endive (4 heads), cut crosswise into 1-inch pieces
Directions
Bring 2 quarts water, 1 tablespoon lemon juice, and 2 teaspoons salt to a boil in a 3-quart saucepan, then poach shrimp at a bare simmer, uncovered, until just cooked through, about 3 minutes. Transfer with a slotted spoon to a bowl of ice and cold water to stop cooking. Let shrimp chill in water 2 minutes, then drain and pat dry.
Whisk together tarragon, mustard, pepper, and remaining 2 tablespoons lemon juice and 1/2 teaspoon salt in a serving bowl. Add oil in a slow stream, whisking until emulsified.
Quarter avocados lengthwise, then pit, peel, and cut into bite-size pieces. Add shrimp, avocados, and endive to dressing and toss.
