01 - In a mixing bowl, whisk together the lemon juice, lemon zest, olive oil, minced garlic, salt, and pepper until well combined. Place the chicken breasts in a resealable plastic bag or shallow dish, pour the marinade over them, and seal tightly. Refrigerate for at least 30 minutes, or up to 2 hours for deeper flavor penetration.
02 - If baking, preheat the oven to 400°F and line a baking sheet with parchment paper. Set a wire rack over the sheet. 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.
03 - Arrange three shallow dishes side by side: in the first, whisk together 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 - Take the chicken breasts out of the marinade and pat them thoroughly dry with paper towels to ensure the breading adheres properly.
05 - Dredge each chicken breast in the seasoned flour mixture, shaking off any excess. Dip it fully into the egg wash, allowing any drips to fall away. Press the chicken firmly into the panko mixture, coating all sides evenly and pressing the crumbs into the surface for maximum adhesion.
06 - For pan-frying: Carefully lay each breaded breast into the hot oil and fry for 3 to 5 minutes per side until deeply golden brown and the internal temperature reaches 165°F. Transfer to a paper towel-lined plate to drain. For baking: Arrange the coated chicken on the wire rack, lightly spray with oil, and bake for 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 before slicing to lock in juices. Garnish with fresh lemon wedges and chopped parsley. Serve immediately.