Bring a pan of salted water to the boil and add the gnocchi. Simmer for 2-3 minutes or until the gnocchi floats to the top of the pan. Once cooked, remove from the pan with a slotted spoon.
Meanwhile, slowly melt the butter in a frying pan. As the butter is melting add the ripped sage leaves followed by a drizzle of oil to prevent the butter from burning.
Once the gnocchi have cooked, remove from the water with a slotted spoon and place into the frying pan with the butter and sage.
Increase the heat and toss the gnocchi into the butter sauce. Squeeze a small amount of lemon juice into the pan to arrest the cooking process then continue to mix for about one minute. If the sauce is too dry, add a splash of the gnocchi cooking water to loosen the sauce.
Remove from the heat and plate the gnocchi using the slotted spoon. Drizzle some of the butter over the gnocchi then grate a generous helping of fresh nutmeg and Parmigiano Reggiano (or an Italian hard cheese of your choice). Complete with a liberal crack of black pepper before serving.
To make the gnocchi
Preheat the oven to 200C/gas 6.
Wash the potatoes, prick them with a fork and rub with olive oil. Place on a baking tray and bake for about 1 hour until crispy on the outside and soft in the middle.
Once baked, allow the potatoes to cool for a few minutes, cut in half and remove the skins. Place the potato flesh into a ricer, bowl or food processor and mash until smooth.
Add an egg yolk to the bowl of mashed potato with a splash of water, sea salt and black pepper. Mix together, gradually adding the flour to reach the desired consistency – like pasta dough. If the mixture becomes too thick, simply add some more water. To test, drop a small piece of dough into boiling salted water; if it breaks, add more flour.
Divide into 6 pieces and roll each piece of dough into cylinders, ensuring that the dough isn’t overworked. Cut each cylinder into 2-3cm pieces with a blunt table knife and place on a bed of semolina flour, on a plate or tray. Leave this in the fridge for 10 minutes to set.