Heat the oil in a deep heavy-bottomed saucepan, until very hot or until a breadcrumb sizzles in it (CAUTION: Hot oil is very dangerous. Do not leave unattended).
Place the flour and sparkling water into a bowl and whisk together to form a batter.
Add the chives and turmeric and mix well.
Dip the onion rings in the batter and then carefully lower into the hot oil and deep-fry until crisp and golden. Carefully remove with a slotted spoon and drain on kitchen paper.
To serve, place onto a serving plate and sprinkle with sea salt.