Cut potatoes into 1/4-inch slices and place in a medium pot. Add chicken broth and bring to a boil over medium-high heat. Reduce the heat to medium, cover and simmer about 15 minutes or until potatoes are tender. In a large bowl, combine green onions, mustard, vinegar, oil, salt and pepper. Add potatoes and combine gently. Cover and refrigerate at least 6 hours or overnight. Drain off excess liquid. Fold in parsley and chives. Serve at room temperature.