Remove neck and other parts from chicken cavity. Save for later. Rinse chicken under cold running water. Place whole chicken in a large stock pot, add cold water to cover by about one inch. Add the neck and other parts that were removed if available. Remove skin from onion, cut in half, add to stock pot with chicken. Add salt. Add black pepper. Place pot over Medium heat on stove top, let come to a boil. REDUCE heat to a simmer, cover pot. Let chicken simmer for one hour, or until chicken is fall off the bone done. Turn off heat, let chicken sit in broth for 30 minutes longer. Remove chicken from pot. Remove the onion from pot. Save the onion for later if desired, or discard. Remove chicken meat from bones, discarding bones and skin. Place 8 cups of chicken stock in another large sauce pot. Place over Medium heat on stove top. Add the chicken. Bring to a slight boil. Add 2 cups of long grain rice. Stir lightly. Bring pot back to a boil. REDUCE heat to a low simmer. Stir well, cover and let simmer for about 15 minutes, or until rice is done. When rice is done, add butter, stir well, remove from heat. Taste for proper seasoning, adding more salt and pepper as desired. Serve warm and enjoy.