1: Preheat the oven to 220°C/Fan 200°C/Gas 7. Line a large roasting tray with baking parchment.
2: Place the squash in the roasting tray. Drizzle with the olive oil, season with salt and pepper and toss to coat. Cook on the top shelf of the oven for 25 minutes or until the squash is tender and browned at the edges. Remove from the oven and let cool slightly for a couple of minutes. (Keep the oven on.)
3: Tip three-quarters of the roasted squash into a blender and blitz to a purée; set the rest aside.
4: Bring a large pan of salted water to the boil. Add the macaroni and cook until almost al dente (2–3 minutes less than the time suggested on the packet).
5: Meanwhile, for the sauce, melt the butter in a large saucepan over a medium heat. Add the flour and cook, stirring, for 1 minute, then whisk in the milk and cook, whisking, until the sauce thickens slightly. Lower the heat and add the liquid aminos, Parmesan and nutmeg. Stir until the cheese has melted, then stir through the squash purée to make a rich, smooth sauce. Take off the heat and season with salt and pepper to taste.
6: Drain the macaroni, add to the sauce and stir well. Tip into a large, deep baking dish, about 25 x 30cm. Scatter over the rest of the roasted squash, the sage, sun-blushed tomatoes and breadcrumbs. Drizzle with the oil. Place on the middle shelf of the oven, turning on the oven grill at the same time. Bake for 10 minutes.
7: Take out the dish, scatter the pumpkin seeds evenly over the surface and return to the oven for 5 minutes or until the topping is golden. Serve at once, with a green salad.