Preheat your oven to 220°C.

To roast the chestnuts, use a sharp paring knife to cut a criss-cross into the flat side of each chestnut. Place them in a roasting pan, sprinkle lightly with water and roast for 20 minutes. Remove them from the oven and wrap in a tea towel until cool enough to handle. Remove the shells and as much of the brown skin as possible.

Peel the potatoes and boil in salted water until soft. Mash well and add the egg yolks, parmesan and flour. Combine until smooth.

Roll the potato mixture into a long tube, approximately 1cm thick and slice into 2cm long rectangles. Roll the rectangles over the tines of a fork and then slightly curl each one. Bring a pot of water to a gentle boil, add the gnocchi and cook until they rise to the surface. Remove with a slotted spoon and keep warm.

Melt the butter in a saucepan. Add the chestnuts, sage, Salt and Pepper and cook until golden brown. Add the gnocchi and toss to coat and heat through. Serve immediately in warm bowls with shavings of parmesan.