Fill saucepan with water and bring to the boil. Add the pasta and cook for 10 minutes or until al dente. Drain, rinse under cold water and set aside.
Grate the mozzarella and parmesan cheese. Finely chop the basil. Place 1 cup of mozzarella, ¼ cup of parmesan, basil, spinach, ricotta, lemon zest, egg, salt, pepper and nutmeg in bowl and combine well with a Spatula.
Preheat the oven to 180°C. Spread half the passata in the base of the casserole dish. Gently fill each pasta shell with the spinach and cheese mixture and place in the container.
Pour remaining passata over the pasta shells, Cover and bake for 30 minutes. Remove from the oven, sprinkle with the remaining cheese and return to the oven, uncovered, for 8-10 minutes until the cheese has melted.
Serve, garnished with fresh basil and extra parmesan cheese.