Rinse and drain the kale well. Steam the kale until it is soft but still colorful, about 5 minutes. Steam the yams until cooked through (they should retain some firmness).
While the kale and yams are steaming, heat the olive oil in a large saucepan over medium-high heat. Add the onion, garlic, ginger, and serrano chile. Cook for 5 minutes, stirring frequently.
Add the cabbage and cook for 5 more minutes, stirring frequently. (Add small amounts of water if necessary to prevent sticking.)
Place the cabbage in a large bowl with the soy sauce and salt; add the kale and mix well. Add the yams and gently mix. Serve with Abba’s African Hot Sauce (recipe elsewhere on this site).