Potato Salad with Grainy Vinaigrette

Place the potatoes and 1 tablespoon of the salt in a large pot. Add enough cold water to cover. Bring to a boil. Reduce heat and simmer until the potatoes are fork-tender, about 25 minutes. Meanwhile, whisk together the lemon juice, honey, shallot, and mustard in a small bowl. Whisking constantly, slowly add the oil in a steady stream. Season with the remaining salt and ¼ teaspoon of the pepper; set aside. Drain the potatoes and cut them into 1-inch pieces. Transfer to a serving dish. Pour half the vinaigrette over the hot potatoes and toss. Set aside for up to 1 hour to allow the flavors to meld. Just before serving, drizzle with the remaining vinaigrette, sprinkle with the remaining pepper and the tarragon, and toss.