Cook your rice, or just using leftover rice.
In skillet, melt butter and sautee onion and celery over medium heat until softened, about 5 minutes.
Once cooked, spoon rice into large bowl. To the rice, add cream of mushroom soup, chicken, vegetables, cream, cooked onion and celery, and salt and pepper.
Spread into a casserole dish. Top with cheese and whatever else you like.
Cover with foil and warm thoroughly at 300 degrees for at least 30 minutes (and up to 60).