Preheat and prep: Preheat your oven to 200°C (180°C fan). Bring a large pot of salted water to a rolling boil — you'll know it's ready when the surface is bubbling vigorously and steam rises steadily. Add the macaroni and cook for 2 minutes less than the package directions (it will finish cooking in the oven). Drain the pasta, reserving about 100ml of the starchy pasta water. You'll see the pasta is still quite firm and pale in the centre.

Sauté the aromatics: In the same large pot, heat the olive oil over medium heat until it shimmers and smells nutty. Add the chopped onion and cook for 4-5 minutes, stirring occasionally, until the onion turns translucent and softens — you'll notice it becomes glossy and releases a sweet, savoury aroma. Stir in the minced garlic and chopped sage, cooking for another minute until the garlic is fragrant but not browned.

Cook the squash: Add the diced butternut squash to the pot along with the stock. Bring the mixture to a simmer — you'll see small bubbles breaking the surface and the stock will look slightly cloudy. Reduce the heat to low, cover the pot, and let it cook for 10-12 minutes. The squash is ready when you can easily pierce a cube with a fork and it feels tender but not mushy; the stock will have reduced by about a third and smell sweet and earthy.

Create the creamy sauce: Remove the pot from the heat. Using a potato masher or a stick blender, mash or blend the squash mixture until smooth — you're aiming for a thick, velvety purée with no lumps, the colour of a deep sunset. Stir in the double cream, grated cheddar, half the Parmesan, salt, pepper, and nutmeg. The sauce will look glossy and smell rich and cheesy. If it seems too thick, add a splash of the reserved pasta water until it reaches a pourable consistency.

Combine with pasta: Add the drained macaroni to the sauce and stir thoroughly until every piece of pasta is coated — you'll see the sauce clinging to the ridges of the macaroni, creating a uniform, golden mixture. Taste and adjust seasoning if needed.

Assemble and bake: Transfer the mixture to a lightly greased 23x33cm baking dish. Sprinkle the remaining Parmesan and the breadcrumbs evenly over the top. Bake for 15-18 minutes, until the top is golden brown and bubbling around the edges — you'll hear a gentle sizzle, and the breadcrumbs will look crisp and toasted. Let it rest for 5 minutes before serving; the sauce will thicken slightly as it cools.