Heat the oil in a deep saucepan to 180°C, or until a piece of bread dropped in turns golden in 30 seconds.
Whisk the baking powder and salt into the chilled flour. Quickly whisk in the cold beer until you have a thick batter. Do all of this just before you cook the fish.
Dip your fish into the batter then, holding it on the slimmer end, very slowly lower it into the oil so the batter starts to instantly puff up, before lowering it fully into the pan. If you let go straight away it will sink to the bottom and stick on the base of the pan.
To serve: Serve the fish with chips, lemon wedges for squeezing over and tartare sauce.
Chips (gf) (v)
Peel and cut the potatoes into chips then place in a large saucepan of salted water. Bring to the boil then cook until the chips have started to soften. Carefully drain and set aside to cool. This can be done well ahead of time
Heat 1cm of oil in a large sauté pan and cook the chips until golden, tender on the inside and crisp on the outside. Drain on kitchen towels and sprinkle with sea salt.
Stir all the ingredients together in a bowl. Makes about ¾ cup.