Healthy Chicken Salad

Ingredients

• 1 teaspoon salt
• 1/2 teaspoon freshly ground black pepper
• 1 pound (2 small whole breasts) boneless, skinless chicken breasts
• 3/4 cup plain nonfat yogurt
• 1 tablespoon dijon mustard
• 2 tablespoons freshly chopped chives
• 1 tablespoon freshly chopped tarragon
• 1 granny smith apple
• juice of 1/2 lemon
• 1 cup finely diced fennel
• 1/2 cup finely diced celery
• 2 cups red seedless grapes, cut in half
• 6 slices pumpernickel bread
• 1 bunch watercress, tough stems removed
• olive-oil cooking spray