Deshell prawns and remove sand veins.
Cut the belly side in 1 cm intervals, half way down the prawns.
Stretch prawns to make them longer along these cuts, but do not break prawns.
Dip into flour, set aside.
Roughly add the iced water together with some crushed ice to the flour, do not mix thoroughly. Some flour should still be visible.
The oil must be super hot, because your batter is ice cold.
From a low height, drop down some batter. You should get tempura bits.
Dip the prawns into the batter and then into the hot oil, it takes just 1/2 minute to cook.
Drain and arrange on plate or in the noodles.