1. Preheat the oven to 350°F 175°C and lightly grease a 9×13 inch baking dish with nonstick cooking spray.

2. If using fresh broccoli, cut it into small florets and steam or microwave for 2 to 3 minutes until bright green and slightly tender, then drain well. If using frozen broccoli, thaw completely and pat dry.

3. In a large mixing bowl whisk together the condensed cream of chicken soup, sour cream, and chicken broth until smooth.

4. Stir in 1 cup of the shredded cheddar cheese along with the garlic, chopped onion, Dijon mustard, smoked paprika, salt, and pepper until everything is evenly combined.

5. Add the cooked shredded chicken, cooked white rice, and prepared broccoli to the bowl and gently fold until the rice and chicken are well coated and the broccoli is evenly distributed.

6. Transfer the mixture to the prepared baking dish and spread it into an even layer.

7. Sprinkle the remaining 1/2 cup shredded cheddar cheese evenly over the top of the casserole.

8. In a small bowl stir together the melted butter and panko breadcrumbs, then sprinkle the buttery crumbs evenly over the cheese layer.

9. Bake the casserole for 30 to 35 minutes, or until the edges are bubbling, the top is lightly golden, and the center is heated through.

10. Remove from the oven and let the casserole rest for 5 to 10 minutes before scooping or slicing and serving warm.