Add the shallots to the skillet and cook over moderate heat, stirring occasionally, until lightly browned. Add the cider and bring to a simmer over high heat, scraping up any browned bits. Return the ham slices to the skillet and cook until warmed through. Transfer the ham to a platter and season with pepper. Boil the sauce until reduced to 1/4 cup, about 2 minutes longer. Pour the sauce over the ham, sprinkle with snipped chives and serve.