Rinse the rice in water several times and soak in water for 20 minutes, drain and set aside. Preheat oven to 375ºF.
Season the chicken pieces with salt, pepper, garlic powder, and paprika. Heat olive oil in a skillet over med-low heat, brown the chicken until golden on both sides, about 5-6 minutes on each side. Transfer to another plate and set aside. If there is too much grease in a skillet wipe out with a paper towel.
In a same skillet saute the mushrooms for 1 minute and splash with wine (or stock) and let it reduced. Transfer the mushroom to another plate as well.
Melt the butter in the skillet and saute the onion, carrot, celery and garlic for 3-4 minutes until slightly soften.
Add the rice and saute 2 more minutes. Pour the chicken stock and cream, add the thyme and stir. Return the chicken pieces to top and cover the skillet with foil tightly. (if your skillet is nor oven proof, transfer the rice mixture to a casserole pan and top with chicken)
Bake the casserole for 45 minutes, and serve hot.