Pat dry the fish using paper towel, getting them as dry as possible.
Peel the swede and cut into french fry shape rectangles.
Cut the onion into 1/2 cm slices, using the outside rings only (I got 6 rings). Save the rest of the onion for future use.
In a large bowl, whisk together the batter ingredients until smooth. It should be the consistency of a thick pancake batter.
In a small, high sided frying pan or wok, heat the cooking oil to 180C over medium high heat. I used a 20cm pan and cooked in 3 batches, and use a thermometer to get the temperature right. Once it reaches 180 turn the temperature to low to maintain this temperature.
In batches of 1 - 2 depending on your pan size, dip the fish fillets in the batter and fry until golden on one side then flip over. This usually takes 2 - 3 minutes per side.
While the fish is frying, you can batter a few chips and fry around the fish. Get them nice and golden and crispy!
Remove the golden fish and chips from the oil with a slotted spoon and place on paper towel.
Batter and fry the onion rings for 2 minutes per side or until golden. Drain on paper towel.
Serve immediately with fresh lemon, extra salt and tartare sauce!