• Preheat the oven to 200°C/400°F/Gas Mark 6.
• Bring a large saucepan of water to the boil, add the leeks and cook for 2 minutes. Add the butternut squash and cook for a further 2 minutes. Drain in a colander.
• Mix the curry paste with the oil in a large bowl. Toss the leeks and butternut squash in the mixture to coat thoroughly.
• Transfer the leeks and butternut squash to a non-stick baking tray and roast in the oven for 10 minutes until golden brown. Add the tomatoes and roast for a further 5 minutes.
• Meanwhile, cook the pasta according to the instructions on the packet and drain.
• Put the sauce into a large saucepan and warm over a low heat. Add the leeks, butternut squash, tomatoes and coriander and stir in the warm pasta. Mix thoroughly and serve.

for the white sauce

• To make the sauce, put the milk into a small non-stick saucepan with the flour, mustard, onion and bay leaf. Whisk over a medium heat until thick. Remove from the heat, discard the onion and bay leaf and stir in the cheese. Set aside, stirring occasionally, to prevent a skin forming.