Make marinara sauce if using homemade.
Sweat the eggplant. Place sliced eggplant on a wire rack, then sprinkle evenly with a few teaspoons of Kosher salt on both sides. Allow the eggplant to sweat for about 10-15 minutes, then flip and sweat for another 10-15 minutes. Use a paper towel to gently wipe any excess moisture off of the eggplant slices.
Set up the dredging station. For this you’ll need 3 shallow bowls. In one bowl, whisk together 6 large eggs with ½ tsp Kosher salt. In the second bowl, combine 1½ cups flour and 1 Tbsp dried oregano. In the last bowl, combine 3 cups breadcrumbs, ½ cup grated Parmesan, 1 tsp Kosher salt, and ¼ tsp black pepper.
Heat the oil. In a large heavy bottom skillet, add enough neutral oil to come up about ½-inch. Heat over medium-high heat until a temperature of ~375F is reached. Meanwhile, prepare the eggplant.
Dredge the eggplant. Dip eggplant slices in flour mixture first, carefully shaking off any excess, then place in the bowl with the eggs. Coat evenly on all sides, allowing excess to drip off before placing in the breadcrumb mixture. Press down firmly to ensure even coating on both sides. Repeat with remaining eggplant.
Cook the eggplant. Working in batches so as not to overcrowd the pan, cook eggplant slices in hot oil for 2-3 minutes per side, or until golden brown. Once done, carefully transfer to the wire rack, then sprinkle lightly with Kosher salt. Repeat until all eggplant is fried, adding more oil in between batches if needed (and waiting for the new oil to come up to temperature. Cold oil = greasy eggplant slices). Allow the eggplant slices to cool for 30 minutes before moving on.
Assemble the eggplant parmesan. Spoon about 1 cup of sauce on the bottom of a 9x13 baking dish. Add a single layer of eggplant slices, then spoon another 1 cup of sauce on top, spreading evenly over the eggplant. Sprinkle with ⅓ of the remaining grated Parmesan cheese and a few fresh basil leaves, ripped into small pieces. Repeat with another layer of fried eggplant slices, sauce, Parmesan, and basil, then add half of the hand ripped mozzarella cheese (about 2 cups). Repeat with remaining eggplant, sauce, Parmesan, and basil, creating 2 more layers, but reserving all remaining mozzarella cheese for the top layer. Once assembled, allow the eggplant parm to rest for 30 minutes.
Bake the eggplant. When ready, preheat an oven to 375°F/190°C. Cover tightly with foil, being sure not to touch the top layer of cheese if possible. If this is unavoidable, spray the foil with nonstick cooking spray to prevent sticking. Bake for 40 minutes, covered, then remove the foil, return the casserole to the oven, and cook for an additional 15 minutes.
Rest, then serve. Allow the eggplant to cool for 30 minutes before slicing. This seems unnecessary, but the layers will slide around if they don’t have a chance to rest and cool. Enjoy with additional grated Parmesan and fresh basil leaves!