Creating Pasta alla Sorrentina is a delightful process that anyone can follow. Here’s how to do it step-by-step:

1. Boil the Pasta: In a large pot of salted boiling water, cook the pasta according to package instructions until al dente. Drain and set aside.
2. Sauté the Aromatics: In a large skillet, heat the olive oil over medium heat. Add the chopped onion and cook until translucent, about 5 minutes.
3. Add Garlic: Stir in the minced garlic and sauté for an additional minute or until fragrant.
4. Prepare the Sauce: Pour in the crushed tomatoes and stir in the salt, black pepper, oregano, and sugar if desired. Let the sauce simmer for 10-15 minutes until slightly thickened.
5. Combine Pasta and Sauce: Add the cooked pasta to the sauce, stirring to combine well. Make sure all the pasta is coated with the sauce.
6. Add Mozzarella: Gently fold in the diced mozzarella, allowing it to mix with the pasta and start melting.
7. Transfer to Baking Dish: Pour the pasta mixture into a greased baking dish, spreading it evenly.
8. Top with Parmesan: Sprinkle the grated Parmesan cheese on top of the pasta.
9. Bake: Preheat your oven to 180°C (350°F). Place the baking dish in the oven and bake for 15-20 minutes, or until the cheese is bubbly and golden.
10. Garnish: Once baked, remove from the oven and let it cool for a few minutes. Garnish with fresh basil leaves before serving.

These steps will guide you to create a Pasta alla Sorrentina that will surely impress your family and friends.