1. Mix together mayonnaise, buttermilk, tarragon, mustard and lemon juice to make a dressing.
2. Combine shrimp, apple, grapes, celery, peas and almonds.
3. Pour dressing over shrimp mixture and fold together.
4. Season with salt and pepper. Serve in lettuce leaf cup.
Tip: Try using plain yogurt or sour cream in place of the buttermilk.