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 large zip-top 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 maximum flavor penetration.
03 - Preheat the oven to 400°F if baking. If pan-frying, heat a large heavy-bottomed skillet with 1/2 inch of vegetable oil over medium-high heat until the oil reaches 350°F.
04 - Arrange three shallow dishes: combine the flour, cornstarch, paprika, cayenne, and garlic powder in the first; beat the eggs with milk in the second; toss the panko breadcrumbs with melted butter and lemon zest in the third.
05 - Remove the chicken from the marinade and pat each piece thoroughly dry with paper towels to ensure proper adhesion of the breading.
06 - Dredge each chicken breast in the seasoned flour mixture, shaking off excess. Dip into the egg wash, allowing any extra to drip off. Press firmly into the panko mixture on all sides to create a complete, even crust.
07 - To fry: cook each piece 3 to 5 minutes per side until deep golden brown and the internal temperature reaches 165°F, then transfer to a paper towel-lined plate. To bake: arrange the coated chicken on a wire rack set over a lined baking sheet, spray lightly with oil, and bake 20 to 25 minutes, flipping halfway through, until crisp and fully cooked.
08 - Allow the chicken to rest for 5 minutes before slicing. Serve garnished with fresh lemon wedges and chopped parsley.