Place potatoes in a medium saucepan and cover with water. Bring to a boil, reduce heat to a simmer, and cook until potatoes are tender. Drain and set aside.
Heat 2 tablespoons oil in a large skillet over medium-high heat. Stir in onion and cook until onions are golden in color, about 8 minutes. Add the ham and continue to cook and stir until the ham begins to brown. Transfer to a bowl and set aside.
Heat remaining 2 tablespoons oil in the same skillet. Add the drained potatoes and saute until browned. Season with salt and pepper to taste. Stir in ham mixture and the parsley. Cook all together for a few more minutes and serve hot, topped with dollops of sour cream.
