An assertive lemon juice vinaigrette infuses the shrimp, creating a tart, bold contrast to the sweet peas and the subtle chervil.
Preheat broiler. Make the vinaigrette: Whisk together chervil, garlic, lemon zest, lemon juice, oil, and salt in a small bowl; season with pepper.
Toss shrimp with 1 tablespoon vinaigrette. Place shrimp on a rimmed baking sheet lined with foil; broil shrimp until cooked through, 3 to 4 minutes. Let cool completely. Refrigerate in an airtight container until ready to use, up to 2 hours.
Combine peas, snow peas, shrimp, and remaining vinaigrette; toss. Refrigerate in an airtight container (or store in a chilled cooler) until ready to serve, up to 3 hours. Toss salad again before serving.
You can use tarragon in place of chervil.