Make the Pesto: Blend olive oil, fresh basil, Parmesan cheese, garlic, and salt to make a coarse pesto.
Prepare the Sauce: In a pan, combine a portion of the pesto with julienned onion. Add tomato passata and cook on low heat. Season with salt and freshly ground black pepper to taste.
Prepare Eggplants: Score halved eggplants, drizzle with olive oil, and bake until soft. Scoop out the flesh and chop to retain some texture.
Make Eggplant Meatball Mixture: Combine eggplant flesh with garlic, chopped parsley, Parmesan, salt, pepper, and breadcrumbs to achieve a moldable consistency.
Form and Fry Meatballs: Form the mixture into balls, chill to firm up, then coat in beaten egg and breadcrumbs. Fry in hot oil until golden.
Serve: Serve the spaghetti with the tomato sauce and eggplant meatballs. Garnish with more Parmesan and optionally, parsley.