Avocado, shrimp and endive salad

This tasty, light salad doesn't involve much cooking, just cooking the shrimp.

3 Tbsp. fresh lemon juice
2-1/2 tsp. salt
1 lb large shrimp in shells (16-20), peeled and deveined
2 ea. Hot House tomatoes Peeled and seeded
1 Tbsp. chopped fresh tarragon
2 tsp. Dijon mustard
1/4 tsp. black pepper
3 Tbsp. olive oil
2 firm-ripe California avocados (preferably Hass)
1 lb Belgian endive (4 heads), separate leaves

Procedure:

1. Bring 2 quarts water, 1 Tbsp. lemon juice, and 2 tsp. salt to a boil in a 3-quart saucepan.
2. Poach shrimp at a bare simmer, uncovered, until just cooked through, about 3 minutes.
3. 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.
4. Whisk together tarragon, mustard, pepper, and remaining 2 Tbsp lemon juice and 1/2 tsp salt in a serving bowl.
5. Add oil in a slow stream, whisking until emulsified.
6. Peel and cut avocado into bite-size pieces.
7. Add tomatoes.
8. Toss gently in a small amount of dressing.
9. Place one shrimp in each leaf, lightly fill and arrange leaves on a serving platter.
10. Drizzle with remaining dressing.
11. Serve chilled