Peel and grate the ginger using a small holed cheese grater. Mince the garlic, and dice the onion. Sauté the onion, ginger, and garlic in a large pot with the olive oil over medium heat for 2-3 minutes, or until the onion becomes soft and translucent.
While the onion, ginger, and garlic are sautéing, peel and dice the sweet potato into 1/2-inch cubes. Add the sweet potato cubes, cumin, and red pepper to the pot and continue to sauté for about 5 minutes.
Add the tomato paste, peanut butter, and vegetable broth to the pot. Stir until the peanut butter and tomato paste have mostly dissolved into the broth. Place a lid on the pot and turn the heat up to high. Allow the stew to come up to a boil. Once it reaches a boil, turn the heat down to medium-low and allow it to simmer for 15-20 minutes, or until the sweet potatoes are very soft.
While the soup is simmering, prepare the collard greens. Use a sharp knife to remove each stem (cut along the side of each stem), then stack the leaves and cut them into 1/2-inch wide strips. Place the chopped collard greens in a colander and rinse very well
Once the stew has simmered for 15-20 minutes and the sweet potatoes are very soft, stir in the collard greens. Let the stew simmer for about 5 minutes more, then begin to smash the sweet potatoes against the side of the pot to help thicken the stew.
