Slice the eggs lengthwise in half, using sharp straight-edge stainless steel knife and making one clean cut; wipe blade in between cuts to keep whites clean of yolk. Carefully separate yolks from whites, placing yolks in a medium bowl as you work.
Place whites on a plate; let stand, loosely covered with dampened paper toweling, then with plastic wrap, at room temperature until ready to fill. Mash yolks with fork until crumbly, add mayonnaise and mash together; fold in celery, shallot, mustard, and vinegar, salt and pepper to taste.
Let mixture set at room temperature for about one hour or so to let flavors blend. Fill whites and tuck the parsley leaves into the side of each egg half. Cover the deviled eggs and put in refrigerator until ready to serve. Just before serving cook bacon and sprinkle on top of each egg.Servings: 12