Wash the potatoes and boil them until tender with the skin on. Drain the water and steam the potatoes well dry. Peel the potatoes and mash them thoroughly with a fork (if you have a potato ricer, this is when it comes into its own) in a bowl. Beat the egg and add it together with the flour, oil, Parmesan, and salt, and knead well with your fingers to form a smooth dough.

Sprinkle a little flour on the countertop and roll the dough into finger-thick sausages. Cut into approximately 1 ½ cm wide slices; the Italians now give them a little press with a fork to create ridges in the gnocchi. Let them rest for about fifteen minutes on a clean and dry kitchen towel, then they are ready for boiling.

Preheat the oven to 180 degrees Celsius (356 degrees Fahrenheit) with fan, spread the Parma ham on baking paper on a baking sheet, and bake the slices in the oven until they are crispy. It takes about 8-10 minutes.

Put a pot on with water. When the water boils, add plenty of salt to the water. Boil the gnocchi until they rise to the surface; it takes 4-5 minutes. Carefully fish them out with a slotted spoon, place them in a colander, and let them drain well.

While the gnocchi cooks, pull the whole sage leaves off the stems, melt the butter in a pan, and fry the leaves gently for 3-4 minutes. The butter should turn golden. Carefully toss the boiled gnocchi in the pan, and heat them through briefly. Arrange in 4 deep plates, remember to include the butter, place the crispy ham slices on top. Grate some Parmesan and freshly ground pepper over – serve immediately.