Cook potatoes in their jackets in a little water with the lid on, virtually steaming them.

Peel while still hot then pass through a ricer and cool. Do not use a blender.

Make a well in centre of potato mound and add a handful of flour, the yolks, salt, nutmeg and 50g parmesan. Fold continuously towards centre, gradually adding more flour until it comes together without being sticky. Allow to rest for 5 minutes.

Shape by rolling some mixture into a sausage shape about 3cm in diameter and cutting off 3cm pieces. Roll each piece on the back of a fork using thumb and forefinger. Once a few have been shaped, test by bringing a small saucepan of water to boil.

Add three or four gnocchi. When they rise, check they aren't too soft or falling apart. If they are, add more flour. To serve, poach gnocchi in a large pot of salted boiling water until they rise to the surface, then scoop on to a large serving plate.

Meanwhile, in a small pot, heat butter on high until it develops a nut-brown colour. Add sage and continue cooking for 30 seconds until leaves are crisp. Sprinkle remaining parmesan and drizzle sizzling butter on to gnocchi.