1 boneless, skinless chicken breast
2 ribs celery
1/2 medium yellow onion
1/4 medium red bell pepper
1 T. mayonnaise
1 t. Dijon or spicy brown mustard
1 t. dried thyme
1/2 t. sugar
Heat broiler. On cutting board, place half of chicken breast between sheets of plastic wrap and pound to 1/4 inch thick; repeat with other half. Pat dry with paper napkins. Sprinkle each side lightly with salt. Place breast halves flat and slightly separated on piece of aluminum foil.
Slip foil and chicken onto cookie sheet or shallow baking pan. Broil, turning once, until browned on both sides and liquid runs clear when punctured.
Let chicken cool 5-10 minutes, then cut into 1-inch chunks. In bowl of food processor with metal blade, combine chicken, celery (cut into chunks), onion (cut into 3 wedges), and red pepper (seeded and cut into chunks).
Process in short bursts until contents are reduced to pieces of 1/4 inch or less. Turn contents into large bowl. Add mayonnaise, mustard, thyme, 1/2 teaspoon salt and sugar.
Mix well and chill 1 hour before using.