Adjust the oven rack to the upper middle position. Set a wire rack inside a large rimmed baking sheet.
Heat the oil in a medium skillet over medium-low heat. Add the breadcrumbs and cook, stirring constantly, until golden brown and fragrant, about 2 minutes. Transfer the breadcrumbs to a plate and let cool for 5 minutes.
In a medium shallow dish, combine the parmesan, salt, pepper, and toasted breadcrumbs. Set aside.
Using a sharp knife, slice both chicken breasts in half horizontally, creating 4 thin fillets. Pat the fillets dry. Working with one fillet at a time, evenly coat each side with the mayonnaise, then move to the breadcrumb mixture, turning to coat and gently pressing to make sure the breading adheres. Place the breaded filets in a single layer on the prepared wire rack. Discard any remaining breadcrumb mixture.
Bake until an instant-read thermometer inserted in the thickest portion of chicken registers 160°F, 20 to 22 minutes, flipping the chicken halfway through. (The chicken will continue to rise to 165°F outside of the oven.) Sprinkle with parsley and more parmesan, if desired. Serve immediately. Love the recipe? Leave us stars and a comment below!
