8ouncesgreen beanstrimmed and cut into two-inch pieces
1large shallotchopped, or ½ cup diced red onion
½cupfinely sliced celeryuse the inside stalks and some of the leaves
1generous teaspoon Dijon mustard
⅛cupwhite balsamic or champagne vinegar
½cupextra virgin olive oil
salt and freshly ground pepperto taste
½cupchopped fresh parsley
2tablespoonsminced fresh dill
Put the potatoes in a large pot; cover with water and boil until tender, about 15 minutes. Drain and rinse with cold water. When cool enough to handle; peel them, if desired, and cut them into bite-sized pieces.
Meanwhile, bring a saucepan of water to a boil; add the green beans, and cook them until crisp-tender, about 5 minutes. Drain and immediately plunge into ice water to stop the cooking process and maintain their bright green color.
In a small bowl, combine the mustard and vinegar. While whisking, slowly add the oil, whisk until fully emulsified.
In a large bowl, combine the potatoes and green beans; season generously with salt and pepper. Pour the dressing over and mix well; add the fresh herbs and mix to incorporate. Cover and refrigerate at least a couple of hours, all day or overnight is best; stirring occasionally.
Remove from refrigerator at least 1 hour before serving.
While this salad can be served immediately, it's best when allowed to set overnight in the refrigerator.