Method

1. For the batter; dissolve the yeast in the lager. Sieve the flour, salt and sugar into a mixing bowl and stir in the beer and yeast mixture. Beat well until everything comes together as a creamy batter. If it's too thick, add a little more lager. Leave on one side for 30 minutes.

2. For the fish; season the fillets with a little salt and pepper and dip in plain flour, shaking off any excess.

3. Heat the oil in a deep fryer and when hot, dip the fish into the prepared batter and lower into the oil. Fry the fish for about 5 minutes, until golden. Drain well on kitchen paper and sprinkle with a little salt.

4. For the chips; peel and cut the potatoes into finger-length chips and transfer to a pan filled with water. Bring quickly to the boil and cook for 2-3 minutes. Drain the chips and spread out onto a tea towel and leave to cool. They can be cooked to this stage well in advance.

5. Heat clean vegetable oil in a deep fryer, over a moderate to high heat. Fry the partially-cooked chips, in batches, in the hot oil, until golden and crisp. Drain well and sprinkle with salt.

6. For the sauce; combine the shallot with the mayonnaise. Pick the dill and parsley leaves from their stalks and chop finely before adding to the mayonnaise. Season with salt and pepper and sharpen with lemon juice. Serve the sauce in pots, sprinkled with cayenne pepper.