Preheat oven to 400°F and lightly grease a baking sheet with olive oil.
Place the chicken breast between two sheets of parchment paper and pound to an even thickness of about half an inch.
In a shallow bowl, whisk the egg. In another shallow bowl, combine the panko, parmesan, sea salt, black pepper, and dried oregano.
Dip the chicken into the egg wash, then press firmly into the panko mixture until fully coated on both sides.
Place the chicken on the prepared baking sheet and bake for 12-15 minutes, flipping halfway through, until the coating is golden and crispy.
Remove from the oven, spoon the marinara sauce over the chicken, and top with the mozzarella cheese.
Return to the oven and broil for 2-3 minutes until the cheese is melted and bubbling.