Preheat oven to 350 degrees.
Add a splash of olive oil to a Dutch oven or large, oven safe pot. Add onions and pork roast and brown both sides over a medium-high flame.
While the meat is browning, mix water, soy sauce, sugar, and spices in a small bowl.
Once the meat is browned, pour the liquid over the meat. Place lid on pot and place in oven. Cook for 1 hour.
Add the cut yams to the pot and use a baster to coat them with the sauce. Place lid back on pot and cook for an additional 30 minutes or until the roast reaches an internal temperature of 160 degrees.