Cook the pasta shells — Bring a large pot of salted water to a rolling boil. Add the shells and cook for 2 minutes less than the packet suggests; you want them al dente and still firm enough to handle. They should feel slightly resistant when you bite one, and the colour will be a pale golden yellow. Drain and rinse under cold water to stop the cooking, then lay them out on a clean tea towel to cool.

Prepare the filling — Heat the olive oil in a large frying pan over medium heat. Add the diced onion and cook until it turns translucent and smells sweet, about 4 minutes. Stir in the garlic and cook for another minute until fragrant. Add the squeezed-dry spinach and cook for 2 minutes, stirring constantly — you’ll see the steam rise and the spinach darken slightly. Remove from the heat and let it cool for 5 minutes.

Mix the cheese base — In a large bowl, combine the ricotta, cottage cheese, beaten eggs, Parmesan, dried oregano, nutmeg, and a generous pinch of salt and pepper. Stir until the mixture is smooth and creamy, with no visible streaks of egg. The texture should be thick enough to hold a spoon upright.

Combine filling — Fold the cooled spinach mixture into the cheese base. Stir gently but thoroughly until the spinach is evenly distributed. You’ll see pale green flecks throughout the creamy white filling. Taste a tiny bit and adjust salt if needed.

Assemble the dish — Preheat your oven to 190°C (fan-assisted). Spread half the passata evenly across the bottom of a large baking dish (roughly 30x20cm). Take each cooled shell and, using a small teaspoon, fill it generously with the spinach-ricotta mixture. Don’t overstuff — you want the filling to sit flush with the edge of the shell, not bulging out. Place each filled shell snugly in the dish, open side up.

Top and bake — Once all shells are arranged, pour the remaining passata over the tops, making sure each shell gets a little sauce. Scatter the torn mozzarella pieces evenly over the surface, then sprinkle an extra handful of Parmesan on top. Bake for 30-35 minutes, until the sauce is bubbling at the edges, the cheese is melted and golden in places, and the kitchen smells deeply of tomato and herbs. If you want a deeper golden crust, switch to the grill for the final 2 minutes — watch it closely so it doesn’t burn.