Prepare the Squash: Preheat your oven to 200°C (180°C fan). Carefully cut the spaghetti squash in half lengthways and scoop out the seeds. Drizzle the cut sides with olive oil and season generously with salt and pepper. Place cut-side down on a baking tray lined with parchment paper.

Roast the Squash: Roast for 30-40 minutes, or until the squash is tender and can be easily pierced with a fork. The exact time will depend on the size of your squash. Once cooked, remove from the oven and let it cool for about 10 minutes until it's safe to handle.

Shred the Squash: Using a fork, scrape the flesh of the squash from the skin. It will naturally separate into long, noodle-like strands. Place the strands in a colander. I find that gently pressing the squash with the back of a spoon helps release any excess moisture, which is key for a creamy, not watery, final dish. You should have about 600-700g of cooked squash. Reduce the oven temperature to 190°C (170°C fan).

Start the Béchamel Sauce: While the squash cools, melt the butter in a medium saucepan over a medium heat. Whisk in the flour and cook for 1-2 minutes, stirring constantly, to form a paste (this is a roux).

Make the Cheese Sauce: Gradually pour in the warm milk, whisking continuously to prevent lumps. Continue to cook, stirring frequently, for 5-7 minutes until the sauce has thickened enough to coat the back of a spoon. Remove from the heat.

Finish the Sauce: Stir in the grated Gruyère, half of the Parmesan (25g), the crème fraîche, Dijon mustard, and grated nutmeg. Season with salt and pepper to taste. Keep stirring until the cheese is completely melted and the sauce is smooth and glossy.

Combine: Add the shredded spaghetti squash to the saucepan with the cheese sauce. Gently fold everything together until the squash strands are evenly coated in that glorious, creamy sauce.

Assemble the Gratin: Transfer the mixture to a 2-litre ovenproof baking dish and spread it out evenly.

Add the Topping: In a small bowl, mix the remaining 25g of Parmesan with the panko breadcrumbs and chopped parsley. Sprinkle this mixture evenly over the top of the squash.

Bake to Perfection: Bake for 20-25 minutes, until the topping is golden brown and the sauce is bubbling around the edges. Let it rest for 5 minutes before serving.