Place the potatoes in a large saucepan and add enough water to cover. Set over high heat, bring to a boil, and boil until the potatoes are fork-tender, about 8 minutes. Drain and set aside.
Meanwhile, heat the oil in a large skillet over medium heat. Add the onion and cook, stirring, until softened, about 3 minutes. Add the fruit along with the juice from the can, the brown sugar, soy sauce, and pepper, bring to a simmer, and simmer until the liquid thickens and reduces slightly, about 5 minutes. Add the ham slices and potatoes and simmer for 2 minutes to heat through. Serve.