Preparation

• Begin by making the pesto. Toast the pine nuts in a hot dry pan until lightly golden and shiny from the natural oils. This should take a few minutes – don't let them burn otherwise they'll taste bitter.
• Add the nuts to a blender along with the Parmesan, garlic, basil, oil and lemon zest and blend to a rough paste (you could also do this in a pestle and mortar). Taste and season with salt, pepper and lemon juice until you're happy with the flavour. Set aside.
• Next, make the béchamel. Heat the butter and flour in a pan and stir to create a paste (this is called a roux). Cook out the roux for a minute or so to avoid a floury taste in your sauce.
• Add the bay leaf then slowly pour in the warm milk, whisking continuously to avoid lumps. The bechamel will start to thicken up after a few minutes. Taste and season with nutmeg, vinegar, salt and pepper.
• Preheat an oven to 180°C/gas mark 4 whilst you assemble the lasagne.
• Choose an ovenproof dish which fits the lasagne sheets (or trim the sheets accordingly). Cover the base with pasta, followed by pesto, then bechamel (discarding the bay leaf in the sauce), repeating this pattern until everything is used up and there is a layer of bechamel on the top. Season each layer with a small pinch of salt and freshly ground black pepper as you go.
• Once layered, sprinkle the top with finely grated Parmesan and some pine nuts. Transfer to the oven and bake for 30 minutes until golden on top, then serve.