Fish Sub Recipe

Prepare rolls

Preheat oven to 350°F (175°C). Slice the sub rolls lengthwise, leaving a small hinge if you prefer. Spread 1 tablespoon of softened butter inside each roll. Place rolls on a baking sheet and warm in the oven for 5–7 minutes until slightly crisp and buttery. Keep warm.

Portion fish

Pat the fish fillets dry with paper towels and cut into portions about the width of the roll (2 pieces per sandwich or one long piece per sandwich), roughly 4–6 oz total per sandwich. Season lightly with 1/2 tsp salt and 1/4 tsp black pepper.

Make batter

In a shallow bowl whisk together the all-purpose flour, cornstarch, baking powder, remaining 1/2 tsp salt, and 1/2 tsp black pepper. In a second bowl beat the egg with the cold sparkling water until combined. Add the egg mixture to the dry mix and stir until a slightly lumpy batter forms. If too thick, add 1 tsp more sparkling water; it should coat the fish.

Breadcrumbs

Place the breadcrumbs in a third shallow dish. These will form a light extra crust when needed.

Fry the fish

Heat vegetable oil in a heavy skillet over medium-high heat to 350°F (175°C) or until shimmering (about 1/4" deep). Working in batches, dip each fish piece into the batter, then lightly press into the breadcrumbs (optional) for extra texture. Carefully lay pieces into hot oil and fry 3–4 minutes per side until golden brown and the fish flakes easily (internal temperature 145°F / 63°C). Do not overcrowd. Transfer to a wire rack or paper towels to drain. Keep warm in the oven with the rolls if needed.

While the fish cooks, combine mayonnaise, chopped dill pickle, chopped capers, lemon juice, chopped dill or parsley, 1/4 tsp salt and 1/4 tsp black pepper in a small bowl. Taste and adjust seasoning. Refrigerate until ready to assemble. This makes more than enough for two sandwiches; reserve extra for serving.

Prepare vegetables

Toss shredded lettuce with a pinch (about 1/8 tsp) of salt and pepper. Slice tomato and onion thinly. Arrange pickles and lemon wedges on a small plate.

Assemble sandwiches

Spread a generous tablespoon of tartar sauce on the bottom half of each warmed roll. Place the fried fish on top (one or two pieces depending on size). Add a layer of shredded lettuce, a couple tomato slices, a few slices of red onion (if using) and 2–3 pickle slices. Squeeze a lemon wedge over the fish for brightness. Close the roll and press lightly.

Serve

Cut each sub in half if desired and serve immediately with extra tartar sauce and lemon wedges on the side.