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 the chicken, seal tightly, and refrigerate for at least 30 minutes or up to 2 hours for deeper flavor penetration.
03 - Arrange three shallow dishes side by side. In the first, combine the flour, cornstarch, paprika, cayenne pepper, and garlic powder. In the second, beat the eggs with the milk until smooth. In the third, toss the panko breadcrumbs with the melted butter and lemon zest until evenly coated.
04 - If baking, preheat the oven to 400°F and line a baking sheet with parchment paper, placing a wire rack on top. If pan-frying, heat 1/2 inch of vegetable oil in a large heavy-bottomed skillet over medium-high heat until the oil reaches 350°F.
05 - Take the chicken out of the marinade and pat each piece thoroughly dry with paper towels to ensure the coating adheres properly.
06 - Dredge each chicken breast in the flour mixture, shaking off excess. Dip into the egg wash, allowing any drips to fall away. Press firmly into the panko mixture on all sides, ensuring complete and even coverage.
07 - For frying: carefully lower each coated breast into the hot oil and cook 3 to 5 minutes per side until deep golden brown and the internal temperature reaches 165°F. Transfer to a paper towel-lined plate. For baking: arrange the coated chicken on the prepared wire rack, mist lightly with cooking spray, and bake 20 to 25 minutes, flipping once halfway through, until the crust is crisp and the chicken is cooked through.
08 - Allow the chicken to rest for 5 minutes before slicing. Garnish with fresh lemon wedges and chopped parsley. Serve immediately alongside roasted potatoes and a crisp green salad.