- Position rack in center of oven, and preheat to 375°F. Coat baking sheet with cooking spray.
- Place flour in pie dish or soup plate. Add panko and Parmesan to second pie dish or soup plate; whisk to blend. Reserve 2 Tbs. panko mixture. Add egg to third pie dish or soup plate; whisk to blend. Season eggplant with salt and pepper, if desired. Coat slices with flour, then egg, then panko mixture; press to adhere. Coat slices on both sides with cooking spray, and arrange on baking sheet.
- Bake eggplant 12 minutes, or until bottoms are brown and crisp. Loosen slices from sheet, and flip over. Bake 12 to 13 minutes longer, or until both sides are brown and crisp, and eggplant is tender.
- Meanwhile, coat large skillet with cooking spray; add spinach. Toss over medium-high heat 2 to 3 minutes, or until wilted. Scrape into towel-lined sieve, and firmly press out excess liquid. Transfer spinach to work surface, and finely chop.
- Recoat skillet with cooking spray. Add spinach, cream cheese, and 1 Tbs. reserved panko mixture. Cook over medium-high heat 3 to 4 minutes, or until mixture is very thick, adding remaining 1 Tbs. reserved panko (if necessary) to thicken.
- Spread marinara sauce atop eggplant on baking sheet. Spoon or spread spinach over top, leaving border of sauce visible. Sprinkle with mozzarella, and bake 4 to 5 minutes, or until topping is heated through.