Steam (or simmer) the potatoes in their skins until tender. Once cool enough to handle, peel them and then directly put through a potato ricer or vegetable mill on to a lightly floured kitchen surface. Allow to cool, then loosely gather the potato together and make a well in the middle with your fingers. Drop in the egg and sift over the flour with the salt. Now gently bring everything together using your hands and knead deftly to a soft dough. At this stage you may need a little more flour, both on the surface and in the mixture. The correct consistency should be similar to soft pastry.

Now roll the dough into long sausage shapes about 2.5cm in diameter, and cut into 2cm pieces. Dust lightly with sifted flour and put on a tray. Refrigerate for 30 minutes, then begin to shape them. Take a fork and, holding it in the left hand, prongs pointing uppermost, pick up one of the pieces of dough. Using your thumb, push the dough down the prongs to make a ridged surface, while simultaneously nicking each piece (a gnocchi) off the tines on to the work surface; this will also form a depression on the other side from your thumb. Once the gnocchi are formed, return them to the floured tray.

Bring a large pan of unsalted water to the boil and drop in about a third of the gnocchi. Simmer until they float to the surface, then give them a further 20-30 seconds. Lift out with a slotted spoon, drain well and place in a heated dish, together with a scrap of butter. Keep warm, cooking the remaining gnocchi in 2 further batches.

Melt the butter with the garlic slices and pine nuts and cook until pale golden. Remove them to a plate, then add the sage leaves to the butter, allowing them to froth and crisp up. Return the garlic and pine nuts. Spoon this buttery mass over the gnocchi, grind over plenty of black pepper and dust with Parmesan. Serve without delay, on hot plates, handing extra Parmesan at table.