Loaded Bacon Ranch Mac and Cheese Casserole

Name: Loaded Bacon Ranch Mac and Cheese Casserole
Ingredients: 2 pkg white Cheddar macaroni and cheese; 4 ounces cream cheese, softened; 6 Tablespoons butter, divided; 3/4 cup milk; 1/2 cup sour cream; 4 ounces sharp Cheddar cheese, shredded, divided; 1 Tablespoon dry ranch dressing mix; 2 cups shredded cooked chicken; 1 12-ounce package broccoli florets, cooked according to package directions; 8 slices bacon, cooked and crumbled; 1/2 cup sliced green onions, divided; 1 cup panko bread crumbs; 1/4 teaspoon freshly ground black pepper