Jalapeño Popper Casserole

Name: Jalapeño Popper Casserole
Ingredients: 4 center-cut bacon slices, chopped; 4 tablespoons unsalted butter, divided; 2 ½ pounds boneless, skinless chicken breasts, cut into bite-size pieces; ½ teaspoon ground pepper, divided; 1 medium yellow onion, chopped; 1 bunch scallions, sliced, white and light green parts separated from dark green parts; 1 cup chopped jalapeño peppers, (about 4 large, seeds and ribs removed), plus 1 jalapeño, sliced; ⅓ cup all-purpose flour; 1 cup no-salt-added chicken broth; 1 cup whole milk; 4 ounces reduced-fat cream cheese; 1 ¼ cups shredded part-skim mozzarella cheese; ¼ teaspoon salt; ¾ cup whole-wheat panko breadcrumbs