01 - In a mixing bowl, whisk together the lemon juice, lemon zest, olive oil, minced garlic, salt, and black pepper until well combined.
02 - Place the chicken breasts in a resealable plastic bag or shallow dish, pour the marinade over them, seal tightly, and refrigerate for at least 30 minutes or up to 2 hours for optimal flavor penetration.
03 - Arrange three shallow dishes side by side: combine the flour, cornstarch, paprika, cayenne pepper, and garlic powder in the first; whisk the eggs and milk together in the second; toss the panko breadcrumbs with melted butter and lemon zest in the third.
04 - If baking, preheat the oven to 400°F and set a wire rack over a lined baking sheet. If pan-frying, heat ½ inch of vegetable oil in a large skillet over medium-high heat until the oil shimmer reaches 350°F.
05 - Remove the chicken from the marinade, pat thoroughly dry with paper towels, then dredge each breast through the flour mixture, dip into the egg wash, and press firmly into the seasoned panko coating, ensuring full and even coverage on all sides.
06 - For pan-frying, cook each breaded breast 3 to 5 minutes per side until deeply golden and the internal temperature reaches 165°F, then transfer to a paper towel-lined plate. For baking, arrange the coated chicken on the prepared wire rack, mist lightly with oil, and bake 20 to 25 minutes, flipping once halfway through, until the crust is crisp and the chicken is cooked through.
07 - Allow the chicken to rest for 5 minutes to lock in juices, then plate and garnish with fresh lemon wedges and chopped parsley before serving.