- Peel and grate the ginger using a small holed cheese grater. Mince the garlic. Sauté the ginger and garlic in vegetable oil over medium heat for 1-2 minutes, or until the garlic becomes soft and fragrant.
- Dice the onion, add it to the pot, and continue to sauté. Dice the sweet potato (1/2 inch cubes), add it to the pot, and continue to sauté a few minutes more, or until the onion is soft and the sweet potato takes on a darker, slightly translucent appearance. Season with cumin and red pepper flakes.
- Add the tomato paste and peanut butter, and stir until everything is evenly mixed. Add the vegetable broth and stir to dissolve the thick tomato paste-peanut butter mixture. Place a lid on the pot and turn the heat up to high.
- While the soup is coming up to a boil, prepare the collard greens. Rinse the greens well, then use a sharp knife to remove each stem (cut along the side of each stem). Stack the leaves, then cut them into thin strips. Add the collard strips to the soup pot.
- Once the soup reaches a boil, turn the heat down to low and allow it to simmer without a lid for about 15 minutes, or until the sweet potatoes are very soft. Once soft, smash about half of the sweet potatoes with the back of a wooden spoon to help thicken the soup. Taste the soup and add salt if needed (will depend on the brand of broth used).
- Serve the stew hot with a few cilantro leaves if desired.
Mustard greens or lacinato kale can be used in place of the collard greens.