Cheesy Chicken, Broccoli, and Rice Casserole

uncooked brown rice (regular or instant)

broccoli florets (can be fresh or frozen, chopped)

¼ cup green onion

olive or canola oil

½ lb chicken breast (cut into small pieces)

½ tsp salt (divided)

¼ tsp pepper (divided)

flour (or 1 TBSP cornstarch for gluten-free)

2% milk

¼ tsp garlic powder

¼ tsp red pepper flakes

¼ cup plain Greek yogurt

½ cups sharp cheddar cheese