4(6-ounce) boneless, skinless chicken breast halves
1cup plain panko breadcrumbs
1/2cup freshly grated Parmesan cheese
1/2teaspoon coarse salt, divided
1/2teaspoon garlic powder
6tablespoons olive oil, divided
4teaspoons fresh lemon juice
Freshly ground black pepper
1/2small red onion, thinly sliced
Preheat oven to 200F.
Cut each chicken breast in half lengthwise, cutting to, but not through, other side. Open up like a book. Place between pieces of plastic wrap and pound to about 1/4-inch thickness.
Place flour in a dish. Combine panko and Parmesan and place in a second dish. Beat eggs with milk and place in a third dish. Sprinkle 1/4 teaspoon salt and garlic powder on chicken. Dredge chicken in flour, shaking off excess, dip in egg wash, then dredge in panko mixture; pat lightly. Transfer to a wire rack 15 minutes to set.
Heat 3 tablespoons oil in a 12-inch skillet over medium-high heat until hot. Add 2 cutlets and cook 2 minutes, or until golden and crisp. Turn and cook 2 minutes more. Transfer to an ovenproof plate and keep warm in oven. Add 2 remaining tablespoons oil (or more as needed), and cook remaining 2 cutlets.
Whisk remaining 1 tablespoon oil with lemon juice in a medium bowl. Add remaining 1/4 teaspoon salt and pepper. Add arugula and onion, and toss. Arrange chicken on serving plates and top with salad.