In a large saucepan heat the oil over medium heat. Add the onion and garlic and saute for about 5 minutes or until the onion is translucent. Add the bell pepper, jalapeno, sweet potato, and tomatoes with their juices. Raise the heat to medium-high and simmer for 5 minutes more. Season the vegetables with salt and black pepper. In a medium bowl whisk together the peanut butter and 1 cup of the vegetable broth until no clumps remain. Stir the mixture into the vegetables along with the remaining 3 cups broth, chili powder, and the cayenne. Cover the pan with a lid and reduce the heat to medium-low. Simmer for 10 to 20 minutes or until the sweet potato is fork-tender. Stir in the chickpeas and spinach and cook until the spinach is wilted. Season with salt and black pepper to taste. Ladle the stew into bowls and garmish with cilantro and roasted peanuts. Tip: Have some leftover rice? The soup is fabulous with some stirred in.