Butterfly each chicken breast by slicing it in half horizontally. Place each cutlet between two sheets of plastic wrap and pound with a meat mallet or rolling pin to about 1/4-inch thickness. Season both sides generously with salt and pepper.

Set up a breading station with three shallow dishes: flour in the first, eggs whisked with milk in the second, and panko mixed with Parmesan, Italian seasoning, and garlic powder in the third.

Dredge each cutlet in flour, shaking off the excess. Dip into the egg mixture, letting the excess drip off. Press firmly into the panko mixture, coating both sides evenly.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. When the oil is shimmering, cook 1-2 cutlets at a time for 3-4 minutes per side until golden brown and cooked through. Add more oil between batches as needed.

Transfer the cooked cutlets to a wire rack. Top with fresh arugula, a squeeze of lemon juice, shaved Parmesan, and a sprinkle of flaky sea salt. Serve immediately.