Heat oil in a large pot or Dutch oven over medium-high heat. Season chicken with salt and pepper, then brown on all sides, about 6 minutes. Remove and set aside.
In the same pot, add onion and bell pepper. Sauté for 5 minutes until softened.
Add garlic and ginger, cooking for 1 minute until fragrant. Stir in cumin, coriander, and cayenne pepper.
Add sweet potatoes and diced tomatoes (with their juices), stirring to combine.
Pour in chicken broth and bring to a boil. Reduce heat to medium-low and simmer for 15 minutes.
In a small bowl, whisk together peanut butter with 1 cup of the hot broth from the pot until smooth. Pour this mixture back into the stew and stir well.
Return chicken to the pot along with chickpeas. Simmer for another 15-20 minutes until sweet potatoes are tender and chicken is cooked through.
Stir in spinach or kale and cook until just wilted, about 2-3 minutes.
Taste and adjust seasoning as needed. Serve over rice or with warm naan bread, topped with chopped peanuts, fresh cilantro, and a squeeze of lime.