60ml/4tbsptomato paste, stirred into 250ml/8fl oz/1cupbeef stock
250ml/8fl oz/1cupdry red wine
115g/4ozchicken livers, trimmed
90ml/6tbsp double/heavy cream
sea salt and ground black pepper
For the White Sauce
pinch of salt
pinch of grated nutmeg
150g/5oz/1½cups freshly grated Parmesan cheese
To make the ragù, heat 115g/4oz/½cup butter in a frying pan and fry the pancetta, carrot, onion and celery until the vegetables are softened. Add the pork, beef and prosciutto and cook until browned. Add the tomato paste and stock mixture and stir, then add the wine. Boil for 1 minute, to evaporate the alcohol, then add the peas, season and reduce the heat. Cover and simmer for 1 hour, then remove from the heat.
Meanwhile, make the pasta. Put the rinsed spinach in a pan with just the water that clings to the leaves, cover and cook for 2 minutes. Drain. Squeeze the spinach as dry as possible. Chop to a purée.
Pile the flour and semolina on to the work surface and blend them together with your fingers. Make a hollow in the middle and pour in the eggs. Add the spinach and work the flour, spinach and eggs to make a smooth, elastic dough. Wrap in clear film or plastic wrap and leave it to rest for 20 minutes.
Meanwhile, make the white sauce. Melt the butter in a pan until foaming, add the flour and mix to a roux. Add the milk and whisk. Add salt and nutmeg. Simmer, stirring frequently, until smooth. Remove from the heat, stir in half the Parmesan, then cover the surface with a little cold water to prevent a skin forming.
Take apple-sized balls of pasta dough and work them through a pasta machine from the widest setting to the narrowest. Alternatively, roll it out as thinly as possible. Cut it into 7.5 x 15 cm/3 x 6 in rectangles.
Cook the lasagna sheets, four at a time, in a pan of salted boiling water for 1 minute. Using a slotted spoon, transfer to a bowl of cold water with the olive oil, to keep them soft and stop them sticking together.
In a separate pan, fry the chicken livers in the rest of the butter until browned, then stir into the ragù. Heat to a simmer, stir in the cream, then remove from the heat. Preheat the oven to 180°C/350°F/Gas 4.
Cover the base of a large, shallow ovenproof dish with a little white sauce. Add a layer of lasagna sheets. Add a layer of ragu, followed by a little Parmesan. Repeat with the remaining ingredients, finishing with white sauce and Parmesan. Bake for 30-40 minutes. Rest for 5 minutes, sprinkle with Parmesan and serve.