Cook the pasta shells: Bring a large pot of salted water to a rolling boil. Add the jumbo shells and cook for 8-9 minutes, until they are al dente — they should feel firm to the bite but pliable when gently squeezed. Drain them and rinse with cool water to stop the cooking, then lay them flat on a baking tray to prevent sticking. You'll notice they have a pale, tender appearance and a slightly springy texture.

Brown the turkey: In a large frying pan, heat the olive oil over medium-high heat until it shimmers. Add the turkey mince and break it apart with a wooden spoon. Cook for 6-7 minutes, stirring occasionally, until the meat turns a rich golden brown and you hear a gentle sizzle. The aroma should be savoury and toasty, with no pink remaining.

Sweat the aromatics: Reduce the heat to medium. Add the diced onion and cook for 3-4 minutes until it becomes translucent and softens, releasing a sweet, mellow fragrance. Stir in the minced garlic and cook for 30 seconds, just until you smell its pungent warmth — do not let it burn.

Wilt the spinach: Add the chopped spinach to the pan in handfuls. Stir continuously for 2-3 minutes, watching as the leaves darken and shrink dramatically, releasing a faint earthy scent. Once all the spinach has collapsed and any excess liquid has evaporated, remove the pan from the heat.

Make the filling: In a large mixing bowl, combine the cooked turkey-spinach mixture with the ricotta, half the grated mozzarella, half the Parmesan, the egg, salt, pepper, and oregano. Stir until everything is evenly incorporated — the mixture should look creamy and slightly chunky, with a pale green hue from the spinach.

Assemble the dish: Preheat your oven to 190°C (170°C fan). Spread half the passata over the bottom of a 23x33cm baking dish. Using a small spoon, fill each cooked shell with about 1½ tablespoons of the filling, pressing gently to ensure it's compact. Place each filled shell seam-side up in the dish, nestling them snugly together. Pour the remaining passata over the tops, then sprinkle the rest of the mozzarella and Parmesan evenly across the surface.

Bake to perfection: Cover the dish with foil and bake for 20 minutes. Remove the foil and bake for another 10-12 minutes, until the sauce is bubbling around the edges and the cheese on top has melted into a golden, slightly blistered crust. The kitchen will fill with a warm, cheesy aroma. Let the dish rest for 5 minutes before serving — this allows the filling to set and the shells to absorb the sauce.