Preheat the oven to 200°C (180°C fan). Bring a large pot of salted water to a rolling boil. Add the jumbo shells and cook for 2 minutes less than the packet instructions—they should still be quite firm to the bite and look pale rather than translucent. Drain and rinse under cold water to stop them cooking further, then set aside.

While the pasta cooks, heat the olive oil in a large frying pan over medium-high heat. Add the cubed butternut squash and cook, stirring occasionally, for 8–10 minutes until the edges are golden brown and the squash feels tender when pierced with a fork. The kitchen will smell sweet and nutty.

Add the chopped onion to the pan and cook for 3 minutes until it turns translucent and softens. Stir in the minced garlic, dried sage, and nutmeg. Cook for 30 seconds until the garlic is fragrant—don’t let it brown or it will taste bitter.

Pour in the chopped tomatoes and vegetable stock. Bring the mixture to a gentle simmer, then reduce the heat to low. Let it bubble away for 5 minutes, stirring now and then, until the sauce thickens slightly and the squash is very tender. You should be able to mash a cube easily with the back of a spoon.

Remove the pan from the heat. Use a potato masher or the back of a wooden spoon to roughly mash about half the squash pieces into the sauce, leaving some chunks for texture. The mixture should look creamy with visible pieces of squash.

In a separate bowl, combine the ricotta, half the grated mozzarella, and half the Parmesan. Season with a pinch of salt and pepper. Stir until smooth—it should look like a thick, fluffy paste.

Spoon about a third of the squash sauce into the bottom of a 23x33cm baking dish. Spread it evenly to coat the base. Now, take each shell and fill it with a teaspoon of the ricotta mixture, then nestle it into the sauce, open side up. Repeat until all shells are filled and snug in the dish.

Spoon the remaining squash sauce over the shells, spreading it gently to cover them. Sprinkle the rest of the mozzarella and Parmesan on top. Bake for 18–20 minutes, until the sauce is bubbling around the edges and the cheese is melted and golden. The top should look speckled with brown spots and the shells will be tender when pierced with a fork. Let the dish rest for 5 minutes before serving—this lets the sauce settle so it doesn’t slide off the shells. Garnish with fresh parsley if you like.