Pat chicken breasts dry with paper towels to remove excess moisture.

Place each chicken breast between plastic wrap and pound to an even 3/4-inch thickness using a meat mallet.

Combine panko breadcrumbs, flour, garlic powder, onion powder, paprika, oregano, salt, black pepper, and cayenne pepper in a resealable plastic bag and shake to mix.

Whisk together the egg and milk in a shallow bowl until smooth to make the egg wash.

Dip each chicken breast into the egg wash, then place into the bag with the breadcrumb mixture and shake to coat evenly.

Heat vegetable oil in a large skillet over medium-high heat until shimmering, about 2 minutes.

Cook the coated chicken breasts in the hot oil for 6 to 7 minutes on the first side without moving to develop a golden crust.

Flip the chicken using tongs and cook for another 6 to 7 minutes until the exterior is golden brown and an instant-read thermometer reads 165°F.

Transfer chicken to a wire rack and let rest for 3 minutes before serving to maintain crispiness.