1. For dressing, in a small bowl whisk together the 1/4 cup oil, the vinegar, sugar (if desired), tarragon, and mustard. Set aside.
2. In a lightly greased 2-quart square foil pan combine potatoes and the 2 teaspoons oil; toss to coat.
3. In a grill with a cover arrange preheated coals around edge of grill. Test for medium-hot heat in center of grill. Place potatoes in center of grill rack. Cover and grill about 25 minutes or just until potatoes are tender. Cool potatoes slightly.
4. In a large bowl combine potatoes, bok choy, radishes, green onions, Canadian-style bacon, and pepper. Add the dressing; toss gently to coat. If desired, spoon the salad into artichoke halves.