For the pasta, put the flour in a large bowl and make a well in the middle. Add the whole egg and yolks and mix with a fork, bringing more flour in from the sides as you mix. When it comes together into a ball, tip out onto a work surface and knead for 10-15 mins until smooth and it bounces back slowly when pressed. Wrap and leave for 20 mins.

To make the filling, tip the spinach into a colander, pour over boiling water, then leave to cool. When cool enough to handle, squeeze out the water with your hands, then again in a clean tea towel to extract as much moisture as possible. Tip onto a board and finely chop. Tip into a bowl with the ricotta, parmesan, garlic, lemon zest and nutmeg, then season well. Scrape into a piping bag with a 1-2cm-wide nozzle.

Cut the pasta dough in half and put both pieces through a pasta machine starting on the widest setting, running the dough through twice on each setting until the second-to-last setting. Lightly flour the work surface and lay the sheets of pasta on it horizontally in a way that enables you to easily lift one sheet over the other later.

Pipe four 7cm wide rings of the filling on the sheet nearest to you, then pipe another four rings directly on top, so you have four 2cm-high ring holders for the egg yolks. Leave approximately 8cm between each. Gently lower an yolk into each ring of filling. Lightly brush the pasta with water around the filling, then lift the second sheet of pasta on top and cup your hand around the filling to gently mould the pasta around it. Try not to leave any air bubbles around the filling. Use a 10cm-round cutter to cut out the ravioli, then carefully lift and pinch the edges together to seal completely. Will keep covered for 30 mins.

Bring a large pan of salted water to the boil and gently lower in the ravioli using a slotted spoon. Boil for 3 mins until the pasta is cooked through, then carefully transfer to two serving bowls.

Working quickly, heat the butter in a large frying pan over a medium-high heat and fry the sage until crisp, about 1-2 mins. Spoon the butter and sage over the ravioli, scatter with more parmesan, if you like, and serve straightaway.