In a large soup pot, heat the olive oil over moderate heat. Add sweet potatoes, onion, and jalapeño, and cook, stirring occasionally with a wooden spoon, until things are softened and tender, about 10 minutes.
Add the ginger, garlic mash, and tomato paste. Stir around and cook until fragrant, a minute or two. Pour in the vegetable broth and water and bring to a boil. Lower heat to maintain a slow simmer, and cook for about 15 minutes.
Ladle about two cups of the hot broth into a small bowl or glass measure. Add the peanut butter and whisk until smooth. Add back to the pot.
Stir the collard greens and chickpeas into the stew and cook for an additional 20 minutes or so, until the stew has thickened and the greens are soft. Serve the stew with chopped peanuts, sriracha or other hot sauce, and a sprinkle of cilantro leaves.