Cut eggplant into 12 even disks, each 1/2 inch thick. (Reserve any leftover eggplant for a scramble or stir fry.)
Lay out a cookie sheet and cover with paper towels. Lay your eggplant evenly on the baking sheet. Sprinkle one tsp salt evenly over one side, flip all of the eggplant, and sprinkle the remaining 1 tsp salt on the other side. Let sit for 1 hour.
Place eggplant in colander and thoroughly rinse off salt. Pat eggplant completely dry.
Preheat oven to 450F. In a shallow bowl, whisk together egg, egg white, cornstarch, and water. On a large plate, mix together breadcrumbs, panko, 2 tbsps parmesan, Italian seasoning, garlic powder, salt, and pepper.
Grease baking sheet with cooking spray. Bread each eggplant disk by dipping into egg mixture, letting excess egg drip off, then placing in breadcrumb mixture. Push breadcrumbs into the eggplant until thoroughly coated, then shake off any excess.
Place breaded eggplant evenly on your baking sheet (3 across x 4 rows). Lightly coat the tops with cooking spray.
Bake eggplant for 8-10 minutes, or until slightly brown (start the marinara now if you plan to make your own). Carefully flip each one, making sure to keep the breading intact. Lightly coat with more cooking spray, then bake for another 6-8 minutes.
Remove eggplant from oven. Top each piece with about 2-3 tbsp of marinara. Sprinkle fresh mozzarella and remaining parmesan evenly over all of the eggplant pieces.
Return to the oven and bake until cheese is bubbly, about 8-12 minutes.
Serve with extra marinara for dipping.