12 fresh spinach lasagne sheets, blanched for 3 minutes in salted water
Make the pasta: Put the spinach into a large saucepan over a medium heat. Add 100 millilitres water and put the lid on until the spinach wilts. Stir then take off the heat and drain. Put the spinach onto a clean teatowel and use it to squeeze as much water out as possible. Leave to cool for a few minutes then blitz to a paste in a food processor. Add the eggs (make sure the spinach isn’t hot or they’ll scramble!) and salt and process to a paste, then add in the flour and pulse until just combined. Tip the dough onto a clean work top and knead for 5 minutes until you have a smooth dough. Wrap the dough tightly in clingfilm and chill for 30 minutes.
Make the pesto: Put the basil, toasted pine nuts, Parmesan, garlic, olive oil and salt into the small bowl of a food processor and blitz to a paste. Transfer to a bowl or jar and cover in the fridge until you’re ready to assemble the lasagne.
Make the vegetable filling: Melt the butter in a large frying pan then add the onion, celery and leek and cook for 5 minutes until starting to soften. Add the courgettes, black pepper and salt and cook until the courgettes are soft and the water has evaporated. Add the spinach in the pan, in batches if needed, until it has all wilted. Stir through and take it off the heat. Leave to cool.
Roll the pasta: Divide the pasta into 4 pieces. Working with one at a time, while the rest is covered with cling film or a damp (not wet) tea towel, put the pasta through a pasta roller on its widest setting. Fold it in half and repeat, six times. This helps guarantee a silky smooth pasta. After six times, turn the machine down by 1 setting and roll the pasta through. Carry on reducing the pasta setting after each roll until the pasta is 1 millilitre thick. Then lightly dust with semolina and leave on a smooth surface or hanging on a pasta rack while you repeat to make enough pasta sheets to layer four full layers of lasagne in your oven dish. Freeze any leftover dough for next time.
Make the béchamel: Melt the butter in a large saucepan then whisk in the flour and cook for 2 minutes. Switch off the heat while you gradually whisk in the milk, until smooth. Turn the heat back on and cook, stirring with the whisk until the sauce thickens. Add in the Parmesan and a big grating of nutmeg and mix until the cheese has melted. Then take it off the heat.
Assemble the lasagne: Preheat the oven to 200C / 180C fan. Combine the vegetables and pesto. Stir through small chunks of mozzarella.
Wipe the inside of the serving dish with olive oil. Put a quarter of the pesto vegetable mixture into the dish and spread it out evenly. Pour over one-fifth of the bechamel and spread it around, then top with slightly-overlapping lasagne sheets - trim them to size if needed. Repeat with the vegetables, bechamel and lasagne sheets, finishing with a layer of lasagne and the final fifth of bechamel. Spread it over the top evenly, then dot with the remaining mozzarella and pine nuts, and grate over the remaining Parmesan. Bake for 35 minutes or until the top is well coloured and the sauces are bubbling. Turn around half way through baking for an evenly-coloured crust. Stand for 45 minutes before serving warm rather than piping hot.