The tarragon dressing can be kept in the refrigerator and used as a sandwich spread or an appetizer dip.

• Prepare and preheat grill. Meanwhile, in a small saucepan, combine the vinegar and tarragon, and bring to a boil. Cook until reduced by half and set aside.

• In a small skillet, melt butter over medium heat. Add shallots and sauté for 5 minutes, or until tender. Transfer to a small bowl and add the mayonnaise, vinegar reduction, and white pepper. Mix well and refrigerate.

• Pound the chicken breasts lightly with meat mallet or rolling pin. Sea-son with salt and pepper.

• Place the chicken on the grill on medium fire and cook, turning once and basting each side with 1 tablespoon of the mayonnaise mixture, for about 7 minutes on each side, or until done. Just before the chicken is ready, place the buns, cut-sides down, on the grill rack to warm.

• Spread the cut sides of the buns generously with the flavored mayonnaise. Place 1 chicken piece on the bottom of each bun. Top with lettuce and tomato and then the bun top. Serve immediately.