Slice the eggplants lengthwise into 1/4-inch thick slices. Sprinkle both sides generously with salt and lay them out on a wire rack or in a colander. Let them sit for 30 minutes to purge excess moisture and bitterness.

Rinse the eggplant slices under cold water to remove the salt, then pat them dry with paper towels.

In a large skillet, heat a generous amount of extra virgin olive oil over medium heat. Fry the eggplant slices in batches until golden brown on both sides, adding more oil as needed. Alternatively, dredge the slices lightly in flour before frying for extra crispness. Drain on paper towels to remove excess oil.

In another skillet, heat 2 tablespoons of olive oil over medium heat. Add the chopped onion and sauté until softened, about 5 minutes. Add the minced garlic and cook for 1 minute until fragrant.

Add the crushed tomatoes, dried oregano, a pinch of salt, and freshly cracked black pepper to the skillet. Let the sauce simmer for 15-20 minutes, stirring occasionally, until slightly thickened. Stir in the fresh basil leaves and remove from heat.

Preheat your oven to 375°F (190°C).

Lightly grease a baking dish with olive oil. Spread a thin layer of tomato sauce on the bottom of the dish.

Layer the fried eggplant slices over the tomato sauce, followed by a layer of mozzarella cheese, a sprinkle of Parmesan cheese, and more tomato sauce. Repeat the layering process until all the ingredients are used, finishing the top layer with tomato sauce and a generous sprinkle of Parmesan.

Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 15 minutes, or until the top is bubbling and lightly golden.

Let the Melanzane alla Parmigiana cool for 10 minutes before serving. Garnish with fresh basil leaves if desired.