Cut the broccoli florets and chicken into bite-size bits. Add this to a mixing bowl. Also add the cooked rice, spring onion, bell pepper and garlic. Stir well.

Add the butter to a small pan. Place it over medium-low heat to melt. Then add the flour. Stir until you get a paste. Cook it for about a minute until it's a little golden. Then add the milk. Turn the heat up. Whisk the mixture firmly while it gets to a boil until it has thickened. Seasoning with a pinch or nutmeg, celery salt, pepper and smoked paprika to taste.

Add the white sauce to the broccoli mixture. Also add about ¾ of the grated cheddar. Keep a handful aside to sprinkle on top of the broccoli casserole later on.

Stir to coat everything in sauce. Pour the broccoli mixture in an oven dish. Spread it evenly. Add the remaining cheddar.

Bake the casserole in a preheated oven at 356°F (180°C) for 30 minutes until the cheese is melted nicely. Divide it over plates. Sprinkle with extra pepper and celery salt. Serve.