Fish Burger with Tartar Sauce

Steps

1. Start with the tartar sauce. Finely chop 40 g of the pickles, the drained capers, the shallot, and the parsley. Stir them into the mayonnaise with the mustard, 1 tablespoon of lemon juice, and a grind of pepper. Cover and refrigerate for at least 20 minutes: the shallot mellows and the flavors come together. Cut the rest of the lemon into wedges.
2. Cut the cod into 4 pieces of 150 g, roughly the size of the bun and an even thickness of about 3/4 inch (2 cm). If one piece is much thicker on one side, slice the thick part horizontally and fold it open like a book to even it out. Pat the pieces very dry with paper towels and season them with half the salt. Let them sit on a plate for 10 minutes.
3. Set up three shallow dishes: the flour mixed with the paprika, the rest of the salt, and the pepper; the eggs beaten with a fork until the whites no longer string; and the panko.
4. Pat the fish dry again, then dredge each piece in the flour, tapping off the excess, dip it in the egg and let it drip for a few seconds, and finally press it into the panko with your palm so it sticks on every side. Set the pieces on a rack and let the coating set in the fridge for 10 minutes.
5. Pour the oil into a large, deep skillet to a depth of about 1/2 inch (1 cm) and heat it to 350°F (175°C) over medium-high heat. Without a thermometer, a cube of bread should brown in about 40 seconds.
6. Fry the fish in two batches, two pieces at a time, so the oil doesn't cool down. Allow 3 to 4 minutes per side, without moving them, until the crust is an even deep golden brown. The fish is done at 136 to 140°F (58 to 60°C) inside: the flesh flakes when you press the side. Drain on a rack set over a sheet pan (not on paper, which makes the crust soggy) and keep warm in a 200°F (90°C) oven while you fry the second batch.
7. While the fish fries, split the buns, butter the cut sides, and toast them in a dry skillet over medium heat for 1 to 2 minutes, until golden. Wash and spin dry the lettuce. Slice the rest of the pickles lengthwise into thin strips.
8. Build the burgers: on the bottom bun, spread a generous spoonful of tartar sauce, then add a lettuce leaf, the breaded fish, a few pickle slices, and a last spoonful of sauce on the top bun. Serve right away with the lemon wedges and the rest of the sauce on the side.