Preparation Stir together onion, vinegar, mustard, 3/4 teaspoon salt, and 1/2 teaspoon pepper in a large bowl. Marinate about 10 minutes. Meanwhile, cook beans in a large pot of well-salted boiling water, uncovered, until just tender, about 6 minutes. Transfer to a large ice bath to stop cooking. Drain and pat dry. Whisk oil and parsley into onion mixture, then toss with beans. What to drink: Artezin Mendocino Zinfandel '07 or Château de Chamirey Mercurey Rouge '07 Cooks' note:Beans can be cooked 1 day ahead and chilled in a sealable bag. Bring to room temperature, then toss with vinaigrette just before serving.
Preparation Stir together onion, vinegar, mustard, 3/4 teaspoon salt, and 1/2 teaspoon pepper in a large bowl. Marinate about 10 minutes. Meanwhile, cook beans in a large pot of well-salted boiling water, uncovered, until just tender, about 6 minutes. Transfer to a large ice bath to stop cooking. Drain and pat dry. Whisk oil and parsley into onion mixture, then toss with beans. What to drink: Artezin Mendocino Zinfandel '07 or Château de Chamirey Mercurey Rouge '07 Cooks' note:Beans can be cooked 1 day ahead and chilled in a sealable bag. Bring to room temperature, then toss with vinaigrette just before serving.