Make salad: Bring a large pot of salted water to a boil. Add all peas and blanch for 3 minutes. Drain and plunge into a large bowl of ice water. When peas are cold, drain and pat dry. Place in a large bowl with radishes.
Make dressing: In a small bowl, whisk together lemon zest and juice, mustard, tarragon and olive oil until well combined; season with salt and pepper. Pour over salad and toss well. Sprinkle with goat cheese.