Preheat oven to 375 degrees. Grease a 2 quart casserole dish.
Over medium heat, melt 2 tablespoons butter and whisk in flour. Cook for 1 minute to get rid of raw flour taste.
Whisk in milk, chicken stock, salt, pepper, onion powder, garlic, tumeric (if using). Bring to a boil then reduce heat. Simmer until sauce has thickened, about 3 to 5 minutes. Turn off heat.
Add in cooked chicken, cooked rice, sour cream, chia and poppy seeds and stir to combine. Pour mixture into greased casserole dish (or leave in pan if using an oven safe dutch oven).
In a ziploc bag, crush up butter crackers. Melt remaining 2 tablespoons of butter and add to cracker crumbs and toss to coat.
Top rice mixture with cracker mixture.
Bake for 20-25 minutes or until crackers have browned.