1. In a pot, melt butter and sauté onion until almost tender. Add mushrooms. Season with 1tsp thyme and salt and pepper
2. Add rice and sauté for 1 minute or until translucent. Add stock. Bring to boil then lower heat. Cover and simmer until rice is tender. Mix midway and fluff rice after cooking.
3. Preheat oven to 350f. stuff rice mixture into cavity of chicken. Tuck wings and tie legs. Set aside extra rice mixture stuffing. Place in an oven-proof dish. Cover and bake for 2 hours until chicken is cooked through. Uncover and roast for another 15minutes to brown chicken. Rest for 10 minutes before slicing. Serve with extra rice mixture.