Chicken Salad Contessa

INGREDIENTS

• 1 tablespoon chopped fresh tarragon leaves, divided
• 1/2 cup walnuts halves
• 1/2 cup pecan halves
• 1 cup green grapes, cut in 1/2
• Kosher salt and freshly ground black pepper
• 2 split (1 whole) chicken breasts, bone in, skin on (1 1/2 pounds)
• Lettuce leaves, for serving
• 1/2 cup sour cream
• Good olive oil
• 1/2 cup good mayonnaise