Curried Chicken Lettuce Wraps

Name: Curried Chicken Lettuce Wraps
Ingredients: 3 boneless, skinless chicken breast halves; 1 onion, sliced; 1 bay leaf; 3 parsley sprigs; 1 thyme sprig; 10 black peppercorns; 1 clove garlic, crushed; 1 tablespoon kosher salt; 1 1/2 cups Greek yogurt; 1/4 cup unsalted roasted cashews; 1/2 cup diced celery; 1/2 cup halved red grapes; 1 1/2 tablespoons curry powder; 1 teaspoon ground ginger; 1/4 cup chutney, such as mango or Major Grey's; 2 tablespoons chopped cilantro; 2 tablespoons chopped scallions; 2 tablespoons chopped basil; Kosher salt and freshly ground black pepper; 8 butter lettuce leaves