Peel 2 potatoes. Cut into small pieces; place in medium bowl. Cut remaining potatoes in half. Scoop out centres, leaving 1/8-inch-thick shells. Chop removed potato pulp; add to chopped potatoes in bowl. Add mayonnaise, vinaigrette, lemon juice, mustard and pepper; mix well. Chop egg finely. Add to potato mixture along with the shallots and 2 tsp. chives; mix lightly.