Preheat the oven to 400 degrees F. Adjust rack in oven so it is in the second from top position.
Line a baking sheet with aluminum foil. Brush with olive oil. Set aside.
Place the chicken breasts, one at a time, into a gallon sized zip top bag, seal it, then pound it to an even thickness using a meat pounder or a rolling pin. You can also place the chicken breasts between two layers of cling wrap instead of a zip top bag if you prefer.
Remove chicken breasts from the bag and pat the chicken breasts dry with a paper towel.
In one shallow dish, mix together panko bread crumbs, grated parmesan cheese, salt, pepper, garlic powder, oregano, and black pepper.
In another shallow dish, whisk the egg.
Dip one chicken breast into the egg, then into the bread crumb mixture. Make sure the chicken breast is fully coated in the crumb mixture, and gently press with your hand to help the crumbs stick to the chicken, flip and repeat with the other side. Place chicken breast on the prepared baking sheet, repeat with remaining pieces of chicken. Spray the top of the chicken with non-stick spray.
Place the baking sheet in the oven on the second from the top rack. Bake for 20-25 minutes, or until cooked through to an internal temperature of 165 degrees F. The cooking time will depend on the size of chicken breast and thickness.
Flip chicken, pour 1/4 cup of marinara sauce over each piece of chicken, then top with grated Mozzarella cheese. Place back in the oven. Turn on the broiler. Broil for 2-4 minutes, until the cheese is melted, bubbly and golden brown and edges of chicken are browning.
Remove from the oven, garnish with chopped parsley if desired.
Serve on top of prepared spaghetti if desired.