Slice eggplant into ¼ inch thick rounds. Layer into a colander, sprinkle with kosher salt, and then weigh down the eggplant with a plate and heavy cans. Let sit for 30 minutes. (It is important to let the eggplant sit weighted down for 30 minutes. This will draw the moisture out of the eggplant.)
While eggplant is sitting, heat olive oil in a skillet over medium heat. Add Panko and cook about 5 minutes, stirring frequently, until Panko is toasted brown. Transfer to a large shallow bowl and cool about 5 minutes. Set up two additional dishes, one with egg white, one with flour.
Add 3 Tbsp Parmesan Cheese, garlic powder, Italian seasoning, and black pepper to the Panko. Mix well.
Preheat oven to 425. Line two cookie sheets with foil.
Blot each eggplant slice with paper towel and remove any excess salt. Dip one face of each eggplant slice in flour (shake off any excess), then egg, and then Panko mixture. Place Panko-side up on cookie sheet. Spray with cooking spray. Cook for 15 minutes or until tender.
In an 8-inch square pan, spread ¼ cup Marinara sauce. Layer half of the eggplant slices. Pour another ½ cup of the Marinara over slices and sprinkle ¼ cup Mozzarella cheese. Layer second half of eggplant slices. Sprinkle remaining 3 tbsp Parmesan cheese, dot ½ cup Marinara over the second layer, sprinkle ½ cup Mozzarella cheese. Bake 10-12 minutes or until cheese is melted and sauce is bubbly.