Heat the vegetable oil in a large soup pot over medium-high heat. Season the chicken pieces generously with salt, pat them dry, and brown them in the oil. Avoid crowding the pot by browning the chicken in batches. Once browned, set the chicken aside.
In the same pot, sauté the sliced onions for 3 to 4 minutes, stirring frequently and scraping up any browned bits from the bottom. Add the minced ginger and chopped garlic, and cook for another 1 to 2 minutes. Stir in the sweet potatoes until well combined.
Pour in the chicken stock, crushed tomatoes, peanut butter, roasted peanuts, ground coriander, and cayenne pepper. Mix thoroughly, then return the browned chicken to the pot. Bring the mixture to a simmer and taste for salt, adjusting as needed. Cover the pot and let it simmer gently for 90 minutes, checking after one hour, until the chicken meat is tender and easily falls off the bone and the sweet potatoes are soft.
Remove the chicken pieces and place them in a bowl to cool until comfortably handled. Optionally remove the skin and discard it, or chop it and return it to the pot. Shred the meat from the bones and add the shredded chicken back into the pot.
Taste and adjust the seasonings, adding more salt and cayenne if desired. Add as much black pepper as you prefer—the stew should have a noticeable peppery kick. Stir in the chopped cilantro and serve the stew on its own or alongside simple steamed rice.