To make the tartar sauce
Fold the gherkins and capers into the mayonnaise with the spring onions dill, parsley and egg. Season with salt and pepper and adjust the acidity with a dash of lemon juice, if you like. Set aside.
To make the battered hake
In a bowl, combine the flour, cornflour, sea salt, baking powder
, fennel seeds and cider, whisking until you form a smooth batter. Set aside.
Fill a medium, heavy-based saucepan two-thirds full with sunflower oil. Heat until a cube of bread browns in 20 seconds.
Cut the hake into chunky strips, about 3cm wide. Season with salt and pepper, then lightly dust with flour.
Dip the pieces of hake into the cider batter then lower them carefully into the hot oil.
Fry in batches (4-5 pieces at a time) for 5 minutes, until crisp and golden brown.
Lift out and drain briefly on kitchen paper.
Sprinkle with flaky sea salt and serve at once with the tartare sauce and lemon wedges.