The mixture of fresh spring peas gives this salad a nice crunch. The smoky-salty bacon and earthy pine nuts add flavor and balance the sweetness of the peas. The peas can be cooked a day ahead, and refrigerated, covered, until serving time.
Combine cold water and ice cubes in a large bowl and set aside.
Bring a large saucepan of salted water to a boil over high heat. Add the snow peas and sugar snap peas, and cook for 90 seconds, then add the shelled peas and continue cooking for 30 seconds more. Drain the peas and immediately plunge them into the bowl of ice water to stop the cooking process. Let them cool for several minutes, then drain again. Transfer the mixture to a salad bowl.
Place the bacon in a skillet, preferably nonstick, and cook over medium-low heat until the bacon is almost crisp. Add the pine nuts and cook, stirring frequently, until the nuts are golden and the bacon is crisp, 2 to 3 minutes. Transfer the bacon and pine nuts with a slotted spoon to several layers of paper towels to drain.
To make the dressing, combine the vinegar, olive oil, tarragon, plus salt and pepper to taste in a glass jar and seal the lid tightly. Shake vigorously to combine.
Just before serving, add the mâche and tarragon to the bowl with the peas. Add the dressing and toss well to combine. Serve immediately.