Green Beans with Mint Vinaigrette and Pickled Onion

Bring a large saucepan two-thirds full of water to a boil over high heat. Add the 1 Tbs. salt and the green beans, and cook until the beans are bright green and tender, 4 to 5 minutes. Drain and immerse the beans in a bowl of ice water to cool, then drain and set aside.

In a small saucepan over medium heat, combine the white wine vinegar, onion, sugar and salt, to taste. Bring to a boil, separating the onion slices into rings, and cook until slightly tender, 1 to 2 minutes. Remove from the heat and let cool.

In a small bowl, whisk together the shallot, mustard, mint and Champagne vinegar. Gradually whisk in 4 Tbs. of the olive oil. Season with salt and pepper and set the vinaigrette aside.

In a large sauté pan over medium heat, warm the remaining 1 Tbs. olive oil and add the beans. Sauté, stirring occasionally, until they are warmed through, 2 to 3 minutes. Drain the onions, discarding the vinegar mixture, and add the onions to the beans. Cook until warmed through, about 2 minutes more. Add the vinaigrette and toss well to coat. Transfer to a warmed serving dish.