Boil the potatoes in abundant salty water, drain, peel and squeeze while still hot in the ricer. Add right away the flour, oil, salt and ground ham. Work the mixture quickly to prevent it from becoming sticky.
With floured hands form many rolls about one finger in thickness and cut into dumplings, not too small in size.
With a light pressure, roll each dumpling over the prongs of a fork.
Flour some trays and arrange the dumplings on them.
Sauce: sauté quickly the Parma Ham cut in strips in butter with the sage. Add pepper.
Boil the dumplings in abundant salted water, drain as soon as they float to the surface and transfer them to a pan containing the sauce, sprinkle with the Parmigiano cheese.