Preheat oven to 400 F. Spread a thin layer of marinara sauce in a baking dish. In a shallow dish, whisk egg and milk together. In another shallow dish, combine breadcrumbs and parmesan cheese.
Dip each egg plan slice in egg mixture, fully coat in breadcrumbs. Place over marinara sauce. Top with the remaining marinara sauce. Bake for 20-25 minutes. Remove from oven, top with cheese. Bake for another 10-15 minutes.