Peel and cut the cassava, sweet potatoes, yams, and plantains into large pieces, about 2 inches thick. Place them in a bowl of water to keep them from drying out while you prepare the soup base.
Remove liver, gizzards and neck from chicken (if included) and set aside or discard.
Using kitchen shears or a sharp knife, cut out the backbone, then split the chicken in half down the center of the breast. You can leave it in halves or cut it into smaller pieces if you prefer. Chop the backbone into 2-3 pieces and set aside.
In a small bowl, mix together the salt, garlic powder, onion powder, turmeric, and parsley. Add the seasoning to the chicken and mix until everything is evenly coated. Let it sit while you start the soup.
Place a large pot over medium heat. Once hot, add the oil, then the onions and a pinch of salt. Cook for a few minutes to let them sweat.
Then add the celery, pumpkin, potatoes, and garlic, and cook for a few minutes. Add the cassava, the seasoned chicken (cut in half) on top along with the backbone pieces, gizzards (if using) and the fresh thyme.
Pour in 8 cups of water and mix everything together. Increase the heat to high and bring to a boil. Once boiling, continue to cook for 30 minutes or until the chicken is cooked all the way through.
After 30 minutes, remove the chicken from the pot and transfer to a bowl. Then remove as much of the skin as possible and shred the chicken into bite sized pieces and set aside.
Remove the thyme stems from the pot and discard. The thyme leaves fall off naturally during cooking.
Using a spoon, crush as much of the white potatoes as you can to help thicken the soup. Then add cooked chicken, sweet potatoes, yam and 2 more cups of water to the pot and continue to cook for another 10 minutes.
Next add in the plantains, carrots and the wiri wiri peppers and continue to cook until the yams and plantains are fork tender (about 10 mintues) and the broth thickens to your liking.
Remove from the heat and serve hot.