Cut each chicken breast half in half horizontally through thickest portion of each breast half. Place chicken between 2 sheets of heavy-duty plastic wrap; pound to 1/8-inch thickness using a meat mallet or small heavy skillet. Sprinkle chicken with salt and pepper.
. Place flour in a shallow baking dish. Combine mustard and egg in another shallow baking dish. Combine panko, parsley, and garlic in a third shallow baking dish. Dredge pounded chicken in flour; dip in mustard mixture, and dredge in panko mixture, pressing firmly to coat.
. Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Add 4 chicken pieces. Cook 3 minutes on each side or until done. Remove chicken, and keep warm. Repeat with remaining 1 tablespoon oil and chicken. Serve with lemon wedges.