Preheat oven to 325 degrees F. Pour uncooked rice in bottom of 9x13-inch baking dish and set aside.

In a medium saucepan melt butter over medium heat. Add flour, chicken bouillon, and black pepper and whisk until clumps form. Cook for a minute to develop flavor, stirring often. 

Slowly add milk and whisk to remove clumps. Heat and continue stirring until mixture thickens. Then add sour cream and water and stir. Set aside.

Prepare chicken by trimming fat and seasoning with salt and pepper (more or less as desired). Place chicken in 9x13-inch baking dish on top of rice and pour sauce mixture over top.

Bake casserole uncovered in preheated 325 degrees F oven. Remove dish from the oven after 45 minutes, carefully remove chicken, and give it a quick stir to redistribute the rice mixture. Then place chicken back in the dish on top of rice mixture and return to the oven.

Test chicken with an instant read thermometer in the thickest part of the breast after it has cooked for 1 hour 15 minutes. Return to the oven if temperature is less than 165 degrees F. Check again after 5 to 10 minutes, if needed, being careful to not overcook. When chicken has reached appropriate temperature, remove from oven and sprinkle fresh or dried parsley on top before serving.