In a bowl, combine flour, salt, baking powder, and baking soda. Mix well and add the water to form a dough.
Coat the hands with 1 tsp of the oil and lightly knead the dough.
Cover with plastic wrap and rest for 20minutes.
Remove from the fridge and turn the rested dough onto a floured surface.
Gently stretch the dough into a rectangle shape and fold into half from bottom to the top.
Then stretch the dough lengthwise and fold it into 3.
Repeat and then roll it into a log.
Leave it in the fridge for at least 2 hours or overnight.
During this time, the dough becomes soft.
When the time comes to cook, remove the dough from the fridge.
Gently stretch the dough to a long rectangular size 2.5cm or 1 inch thick, 7.5 cm wide and 45cm long. You may use a rolling pin to give an even thickness.
Leave the dough to rest while you prepare the cocking oil.
Pour the cooking oil into a pan to at least 2.5cm or 1 inch height. Heat the oil to about 180Cto 220C (average tempt is 200C)
Then cut the sheet dough crosswise into 5cm or 2 inches strips.
Dap the edges of the cut dough with flour to prevent it from sticking.
Wet a skewer or a chopstick with water and wet the centre of a piece of the strips. Wet alternate strips.
Stack two strips together, and press a chopstick in the middle lengthwise.
Hold both ends and stretch the slack strips, then carefully lower it into the oil (be careful not to splash). When it comes up to the surface, roll it around continuously with a pair of chopsticks. Fry the you tiao until it stops expanding and is evenly golden. Repeat the procedure to cook the rest of the dough.
Serve hot or cold.