Peel the potato and slice thinly (just less than half an inch thick). Since we're not parboiling the fritters the potato slices need to be thin enough to soften in the same time it takes our batter to turn golden and crispy. Add the potato slices to a large bowl, cover with fresh water and agitate gently by hand. Drain the cloudy water and repeat once more. Drain again and set the potato slices on a clean kitchen towel or kitchen paper and dry thoroughly.

Put two generous tablespoons of the plain flour on a plate. In a bowl, add the remaining plain flour, cornflour, sea salt and bicarbonate of soda. Mix briefly. Slowly add the lager or beer, adding more or less as necessary and whisking thoroughly until a smooth batter is formed. The consistency of the batter should be similar to single cream.

Heat oil for deep frying to 180C. Working one at a time, press each potato slice into the plain flour on the plate, dusting off any excess, then dip into the prepared batter until completely coated and drop carefully into the hot oil. Cook the fritters in batches and don't overcrowd the pan.

Fry the fritters in the hot oil until golden and crispy, about 3-4 minutes, turning once or twice. Remove the crispy fritters from the oil with tongs or a slotted spoon, drain off any excess oil and arrange on a serving plate. Season generously with your choice of salt, vinegar and brown sauce and serve.