Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.

Steam or blanch the broccoli florets for 2–3 minutes until just tender. Drain and set aside.

In a large mixing bowl, combine the mayonnaise, sour cream, lemon juice, garlic powder, salt, and pepper. Stir until smooth and creamy.

Fold in the cooked shredded chicken and steamed broccoli, gently mixing until well coated with the sauce.

Spread the chicken and broccoli mixture evenly into the prepared baking dish. Top with shredded sharp cheddar cheese.

In a small bowl, mix the panko breadcrumbs with melted butter. Sprinkle the buttery crumbs over the top of the casserole.

Bake uncovered for 25–30 minutes or until hot and bubbly and the topping is golden brown.

Allow to cool slightly before serving. Enjoy with a side salad or over rice if desired!