1. In a pot make the stock by adding the chicken, the onion scraps, celery scraps, the carrots and 5-6 cups of water and bringing it just to the boil. Simmer over medium low heat so it stays just at or below a very slow boil for about 45 minutes or until you think it's done. Remove the pot from the heat and let it cool down a bit, maybe about 30 minutes. This cool down is not absolutely necessary but I think it helps make the stock richer. Onion scraps should include the skins as long as they are undamaged and the celery scraps should absolutely include leaves.
2. While the chicken is cooling, preheat the oven to 375. Cut the sausages in half lengthwise and place face down on a rack over a sheet pan. Bake in the oven until they're crisp. This may take 15 to 30 minutes and you can decide how crisp you want them to be. I like them to be like bacon and don't worry if they look like they are dried out a bit, they will come right back to life when you add them to the stock and they won't bring all that fat into the dish. Just don't burn them and you will be fine.
3. Once cooled, take the chicken out of the pot and remove the meat from the bones. You do not need to cut up the chicken any more than it already is as it will break up on its own in the dish.
4. Heat the oil in a heavy skllet with deep sides or in a cast iron dutch oven. Enameled cast iron such as Le Creuset works best here I think. Add the onion, celery, bell pepper and garlic and cook until translucent. Do not overcook and do not brown this.
5. Stir in the rice and cook for a minute or two.
6. Add the tomatoes if you are using them and stir in with the rice and vegetable mixture. Cook for 1 minute. This is more of a Creole touch but if you like them, add them sparingly.
7. Add 2 c of the stock, the chicken and the sausage to the pot and stir.
8. Add the seasonings and stir.
9. Cook uncovered over medium low heat so you maintain a slow simmer until the rice is cooked and the liquid is absorbed. If it gets too dry and the rice is not cooked add some more of the stock. You want this to be somewhat on the dry side and that's about all I can say. Moe would have to tell you the rest. When it's done add a handfull of chopped parsley and stir that in.