Bean Salad With Bacon and Chives

Cook the bacon in a large skillet over medium heat until crisp, 12 to 15 minutes; crumble, cover, and set aside at room temperature. Toss together the beans, vinegar, oil, and mustard and season with ½ teaspoon each salt and pepper. Refrigerate for up to 8 hours. Just before serving, toss with the chives and bacon.