Roasted pumpkin mac 'n' cheese

Instructions

1. Preheat the oven to 220°C (430°F). Arrange the pumpkin chunks on a large baking tray. Drizzle with 2 tablespoons of the olive oil, and sprinkle with salt and pepper. Roast for about 20–30 minutes, or until soft to touch and dark brown in colour.
2. Meanwhile, in a saucepan, heat the remaining olive oil over low heat and slowly caramelise the onions, stirring often, for about 15 minutes, until browned. Stir in the butter, cook for a few minutes more, then set aside.
3. While the onions are slowly caramelising, cook the pasta in a large saucepan of salted, boiling water until almost al dente, but drain it 1–2 minutes before you normally would, as it will continue to soften in the oven. Drain the pasta in colander, run cold water over it and set aside.
4. Add the flour, nutmeg and tarragon to the caramelised onion mixture and stir well. Pour in the milk and stock, and stir the sauce over medium-low heat until it comes to a simmer and begins to thicken. Add the roasted pumpkin and mix well. Remove from heat. 
5. Using a stick blender, whiz the onion and pumpkin mixture until it is completely smooth. Alternatively, you could transfer the mixture to a food processor or blender.
6. Add the cheddar and parmesan to the sauce and stir until melted. Taste and season to your liking.
7. Combine the pasta and sauce in a large baking dish. Top with the sage, walnuts and extra cheddar. Drizzle with more olive oil and sprinkle with salt and pepper.
8. Bake for 10 minutes, or until the cheddar is melted and the sage is crispy. Serve garnished with fresh herbs if desired.