Over a medium heat, warm the oil in a medium pan (the oil should come about one-third up the sides). When a cube of bread sizzles to a quick copper, you can fry your battered herbs.
Quickly mix the flours, salt, egg yolk and sparkling water together in a large bowl to form a batter; don’t worry about any lumps. Dip the herb into the batter and lower carefully into the hot oil. Expect patchy batter coverage; it is as it should be. Ninety seconds should be enough to fry them perfectly.
Fish out onto kitchen paper, using a slotted spoon. Shower with salt and eat in a hurry.