Into a mixing bowl toss the flour, baking powder, egg, seasoning of choice, stir.
Then add the soda water - it will fizz up a fair bit so make certain you use a deepish bowl.
Coat the fish well in the rice flour, then, when the oil is hot, dredge the fish in the batter and carefully place straight in the hot pan.
Turn after approx. 5 mins.
This is a pleasantly light batter that doesn't over-power the fish but compliments it nicely.
Serve with simple potato wedges, sour cream - or a dollop of Greek yoghurt for the healthier option - on a bed of rocket, dill and sauteed fennel.