Cook the potatoes and pumpkin in boiling water for 20-25 minutes, or until soft, then drain. Mash well and place in a large bowl.
Make a well in the centre and add the egg, salt and freshly ground nutmeg, ¾ of the grated Grana Padano and flour.
Mix by hand to form dough, and then knead for a few minutes.
Cut the dough into smaller pieces and roll each piece into a cylinder.
Cut each cylinder into 2.5cm/1in pieces.
Place the gnocchi in boiling salted water.
When they rise to the top, remove from the saucepan with a slotted spoon and refresh in iced water. Drain, drizzle with olive oil and keep warm.
In the meantime deep fry the sage leaves in a deep fryer or in a pan with very hot oil. Separately sweat the shallots and butter in a pan and then add and sauté the gnocchi.
Sprinkle the extra Grana Padano on top and serve with a crispy fried sage leaf.