Begin by peeling the brown layer on the surface of the yams and wash them thoroughly. Chop the yams into chunks and place them in a pot. Add enough water until the yam pieces are almost completely covered.
Place the pot over high heat and bring to a boil. Cook for about 30 minutes, until the yams become fork-tender. Reserve the cooking liquid as we might need it when pounding the yam.
Pounding the yam with a mortar and pestle:
Once the yam has fully cooked you can transfer a few pieces at a time in a mortar and pestle and pound them to a paste, adding a little of the cooking liquid as necessary to get a smooth and soft consistency.
For pounding, t's best to use yams that have been harvested at least 3 months before cooking. Freshly harvested yams are best processed in a blender.
Using a blender:
Once the yam has softened, transfer the pieces to a food processor and blitz blend stirring with a spoon to make sure all lumps are broken down. Add cooking water as necessary to create a smooth dough-like paste. Fresh yams in the early season of the harvest will take less water while yams harvested in the later season will require more water.
Shape the yam balls by scooping 2-3 spoonfuls into a plastic sheet and molding it into a ball.