Wash the chicken and drain. Place it in a pot, add enough water to cover the chicken, and place over high heat.
Spoon off the scum as it appears. Once the water reaches a boil, add the onion, cardamom pods, and bay leaves. Reduce the heat to low, cover the pot, and simmer for 2 hours, or until the chicken is fully cooked and tender enough to fall off the bone.
In the meantime, wash, drain, and roughly chop the sweet potato leaves.
Remove the chicken with a slotted spoon. Debone the chicken and cut the meat into medium-sized pieces. Set the broth aside.
Add the palm oil to a large stockpot and place over medium-high heat.
Stir in the chopped onions and cook until translucent. Add the chopped sweet potato leaves in batches, continuing to stir and toss as you sauté them.
Pour 3 cups of the chicken broth over the wilted sweet potato leaves. Season with salt and add the whole red peppers.
Add the chicken pieces and chicken bouillon, and stir well.
Once the mixture comes to a boil, reduce the heat to low, cover the pot, and simmer for 2 hours.
Transfer the mixture to an ovenproof dish and bake in a preheated oven at 200°C/400°F for 15–20 minutes, or until the sauce has reduced and thickened.
Serve with plain rice or fufu.