1 tbsp gherkins, roughly chopped
squeeze lemon juice
small handful parsley, finely chopped
8 large Maris Piper potatoes, peeled and cut into chunky chips
½ red onion, chopped
1 tbsp Dijon mustard
1 tbsp capers, roughly chopped
4–5 green olives, chopped
12 tbsp plain flour
6 tbsp cornflour
pinch salt
200ml/7fl oz vegetable oil, plus extra for deep-frying
3 tbsp white wine vinegar
2 egg yolks
4 x 150g/5½oz cod (or haddock) fillets
200ml/7fl oz ale