Preheat the oven to 180°C /Gas Mark 4.
Place the milk, olive oil spread, flour and bay leaf in a saucepan, season, and whisk together over a medium heat continually until it comes to simmering point and has thickened. Turn the heat down to its lowest possible setting and allow the sauce to cook gently for 5 minutes. Then, stir in most (50g) of the Parmesan, remove the pan from the heat and discard the bay leaf.
Heat the olive oil in a large frying pan, add the leeks and red peppers and cook until softened (approximately 5 minutes). Transfer into a large bowl and stir in the ricotta and cashew nuts. Season with black pepper and a pinch of salt.
Assemble the lasagne by spreading one-quarter of the sauce into the bottom of the dish, then one-third of the leek mixture and place sheets of lasagne on top of this. Repeat the whole process, this time adding one-third of the grated Mozzarella, then the lasagne sheets. Repeat again, finishing with a layer of pasta, the rest of the sauce and the remaining parmesan and mozzarella.
Bake for 50-60 minutes until the top is golden and bubbling.
Our thanks to British Leeks for supplying this recipe
Visit our vegetarian recipe section for more meat-free meal ideas, or try one of our other pasta recipes, including vegetarian courgette caponata and smoked tofu and watercress cannelloni.