Prep the oven and pan: Heat oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with cooking spray or a thin layer of olive oil.
Quick-cook the broccoli: If using fresh, steam or microwave for 2–3 minutes until bright green and just tender. If using frozen, thaw and pat dry so extra moisture doesn’t water down the sauce.
Sauté aromatics: In a skillet over medium heat, melt butter.
Add onion and cook 3–4 minutes until soft. Stir in garlic for 30 seconds until fragrant. Remove from heat.
Make the sauce: In a large bowl, whisk together cream of chicken soup, sour cream, chicken broth, Dijon, paprika, garlic powder, onion powder, salt, and pepper.
Stir in the sautéed onions and garlic.
Combine the base: Add cooked rice, chicken, and broccoli to the bowl. Fold in 1 cup of the shredded cheddar. Mix gently until everything is coated.
Assemble: Spoon the mixture into the prepared baking dish.
Smooth into an even layer.
Add the topping: Sprinkle the remaining 1/2 cup cheddar on top. If using panko or crackers, toss them with a drizzle of olive oil and scatter over the cheese for extra crunch.
Bake: Cover with foil and bake 15 minutes. Remove foil and bake another 10–15 minutes, until the casserole is bubbling and the top is golden.
Rest and serve: Let it sit for 5–10 minutes to set.
Taste and add a pinch of salt or pepper if needed. Garnish with chopped parsley if you like.