In a shallow bowl combine grated Parmesan, panko breadcrumbs, chopped parsley, lemon zest, garlic powder, 1/2 tsp salt, and 1/2 tsp black pepper. Stir until evenly mixed. Use a fork to break up any large clumps so mixture is crumbly and cohesive.

Fish & binding

Prepare fillets

Pat the flounder fillets dry with paper towels. Season both sides lightly with 1/2 tsp salt and 1/4 tsp black pepper.

Set up dredging station

Place the flour in a shallow dish. In another shallow bowl whisk together the eggs and milk until combined.

Coat fillets

Lightly dredge each fillet in flour, shaking off excess. Dip into the egg wash, letting excess drip off, then press the top side of the fillet into the Parmesan crust mixture to form an even coating. Press gently so the crust adheres. Place crusted fillets on a plate and let rest 5 minutes to help bind.

Cooking & finishing

Pan-fry fillets

Heat a large nonstick or stainless-steel skillet over medium heat. Add 1 tablespoon butter and 1 tablespoon olive oil. When butter is melted and foaming and oil shimmers, add fillets crust-side down. Cook undisturbed for 2½–3 minutes until the crust is golden brown. Carefully flip and cook 1½–2 minutes more until fish is opaque and flakes easily (internal temp ~ 135–140°F / 57–60°C). Work in batches if needed to avoid crowding.

Finish with butter and lemon

Reduce heat to low, add remaining 1 tablespoon butter to the pan; tilt the pan and spoon the melted butter over the fillets for 30–45 seconds to baste and gloss the crust. Remove fillets to a warm plate. Sprinkle with fresh lemon juice and garnish with chopped parsley. Serve immediately with lemon wedges.