For the crispy potato croquettes with ham, quarter the peeled potatoes, place in plenty of salted water and boil until soft. Drain and allow to steam out briefly.
In the meantime, cut the ham into fine cubes. Press potatoes through a potato ricer or grate on a grater. On a work surface or in a bowl, flavor with salt, oregano and grated Parmesan. Work with ham, eggs, yolks, butter and enough flour to make a compact dough.
“Pick off” small pieces and form into croquettes between the palms of your hands.
Turn in beaten egg and roll in bread crumbs.
Fry in a large, deep pan in hot oil in several tranches, one after the other, until crispy all over.
Remove with a slotted spoon and drain on paper towels.
Serve as a side dish or with salad as a simple main course.