Pat the fish fillets dry with paper towels. Place them on a tray and brush both sides with lemon juice and olive oil. Sprinkle minced garlic, 1 tsp salt and 1/2 tsp black pepper evenly over the fillets. Let rest at room temperature for 10–15 minutes (or refrigerate up to 30 minutes). Pat again briefly with paper towel before coating to remove excess moisture.

Crispy Coating

Make Batter

In a medium bowl whisk together 3/4 cup flour, 1/4 cup cornstarch, 1/2 tsp baking powder, 1/4 tsp salt and 1/4 tsp pepper. In a separate small bowl lightly beat 1 large egg, then whisk egg into the dry mixture. Gradually add 1/2 cup cold sparkling water and the optional 1/4 cup cold beer (or additional sparkling water) while whisking until you have a lump-free, slightly thick batter that coats the back of a spoon. Keep batter cold — place bowl over another bowl with ice if you have it.

Optional Panko Finish

If using panko, mix 1 cup panko breadcrumbs with 1/4 cup grated Parmesan in a shallow dish. After battering the fish, press fillets gently into the panko to create an extra crunchy crust. This step is optional but recommended for extra texture.

Pan-fry / Oil

Heat Oil

In a large heavy skillet (cast iron or stainless) heat 1/2 cup neutral frying oil over medium-high heat until shimmering but not smoking (about 350–375°F / 175–190°C if using a thermometer). Add 1 tablespoon butter just before frying to give flavor; swirl to combine.

Fry the Fish

Dredge each marinated fillet lightly in a small dusting of flour (optional; helps batter stick), then dip into the cold batter, allowing excess to drip off for 5–10 seconds. If using panko, immediately press the battered fillet into the panko mixture to coat. Carefully lay fillets in the hot oil without overcrowding — work in batches if needed. Fry 3–4 minutes per side for 1-inch thickness (longer for thicker fillets) until the coating is deep golden brown and the fish registers 135–140°F (57–60°C) or flakes easily. Use tongs or a slotted spatula and flip once. Adjust heat as necessary to maintain even browning without burning.

Drain

Remove cooked fillets to a wire rack set over a baking sheet or paper towels to drain. Lightly season with a pinch of sea salt while still hot. Keep warm in a 200°F (95°C) oven if frying in batches.

Serve & Garnish

Transfer the crispy fish to a serving platter. Sprinkle chopped fresh parsley over the fillets and serve with lemon wedges on the side. Add additional sea salt and freshly ground black pepper to taste. Serve immediately while hot and crunchy.