Rinse the chips under cold running water then place in a large pan of salted cold water and bring to the boil over a medium heat. Cook for 4–6 minutes or until just tender, then drain well and set aside.

Pat the fish dry, squeeze over a little lemon juice and lightly season with salt and pepper. Lightly dust the fillets with flour.

Sift the flour, salt, baking powder and cayenne into a large bowl. Stirring continuously with a whisk, gradually add enough beer to make a thick, shiny batter (you may not need all the beer).

In a small saucepan over a medium heat, bring just enough water to cover the peas to the boil. Add the peas and cook for 2–3 minutes until tender. Drain, reserving a little of the cooking water, and place the peas in a food processor. Add the butter, a tablespoon of the reserved cooking water, the mint and chilli and pulse until you reach the desired consistency, adding a little more cooking liquid if needed. Season to taste and keep warm.

Heat enough oil for deep-frying in a deep-fryer or deep heavy-based saucepan, making sure it comes no more than two-thirds of the way up the saucepan, to 180°C. If you don’t have a thermometer, test with a drop of batter: it should sizzle and crisp immediately.

Pat the chips dry with a clean tea towel or kitchen paper and gently add to the hot oil. Fry for 3–5 minutes until just starting to colour. Remove and drain well on kitchen paper.

Dip the floured fish in the batter, making sure it is well covered. Carefully lower the fish 1 or 2 at a time into the hot oil and cook for 6–8 minutes, depending on thickness, until crisp and golden.
Remove, drain on kitchen paper, season with salt and keep warm.

Return the chips to the hot oil and fry for 3 minutes or until crisp and golden. Drain well on kitchen paper and season with salt.

Serve the fish hot with the chips and mushy minty peas, with lemon wedges or vinegar and your favourite sauce for dipping.