Kale and Artichoke Chicken Casserole

Name: Kale and Artichoke Chicken Casserole
Ingredients: Kosher salt; 4 bunches Tuscan kale, tough center stems removed, leaves chopped into 2-inch pieces; 3 to 4 tablespoons extra-virgin olive oil; 2 pounds skinless, boneless chicken breasts, cut into 1/2-inch pieces; Freshly ground black pepper; 1 large onion, finely chopped; 1/4 cup all-purpose flour; 1 1/2 cups whole or 2% milk; 2 cups low-sodium chicken broth; 16 ounces frozen artichoke hearts, thawed and roughly chopped; Pinch of cayenne pepper; 1/2 cup grated parmesan cheese; Cooking spray; 1/4 cup panko