Heat the oil in a large pot or Dutch oven over medium heat.
Add the diced onion and cook for 3-5 minutes, until softened and translucent.
Stir in the minced garlic and cook for another minute until fragrant.
Pour in the vegetable stock, then add the sweet potatoes, chickpeas, brown rice, and salt.
Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and let it simmer for about 45 minutes, or until the rice is tender and has absorbed most of the liquid.
In a small bowl, whisk the peanut butter with a ladleful of the hot liquid from the stew until you have a smooth, creamy paste.
Stir the peanut butter paste back into the stew.
Add the sliced kale, lemon juice, and black pepper.
Cook for another 5 minutes, until the kale has wilted.
Season to taste with tamari and hot chili pepper sauce, if using.
Adjust any other seasonings as needed and serve hot.