defrosting cooked chicken casserole thing

Not Hazel, but yes. Doesn't matter if you do it in the oven, in the microwave, in a sinkful of water or by sitting on it like a broody hen ? if it's hot through it will be fine. In fact, as it was cooked before being frozen it would probs be fine even if not hot through.

I d defrost it in the microwave for about 15 mins, then give it a blitz on high. cheaper than using the oven too.