Chill your batter ingredients at least 30 minutes before you start the recipe. 75 ml water and 50 ml carbonated water in the fridge, 15 g cornstarch and 75 g unbleached cake flour in the freezer.
Heat your cooking oil for deep frying to 180 °C (356 °F). While you wait, cut the hard base off of the 200 g enoki mushrooms, but leave some of the white base attached so they don't fall apart.
Tear the enoki into small bundles by hand. Half and half again until you have 8 bundles in total, and pat them thoroughly dry with kitchen paper.
When the oil is almost ready, pour the water and carbonated water into a mixing bowl and add 1 egg yolk. Whisk until combined.
Add the chilled flour and starch one-third at a time, draw crosses with chopsticks to incorporate it and stop mixing as soon as there is no more dry flour (it's okay to have lumps). Add 2 ice cubes if your cooking environment is warm.
Place 2 tbsp unbleached cake flour in a container and use a pastry brush to dust it over the enoki bunches.
Once the oil is preheated, take a bunch of enoki, pinch the base and fan the caps open.
Briefly dip it into the batter, then place it straight into the oil. Fry 2-3 at a time, don't overcrowd the pot.
Fry for about 90 seconds to 2 minutes, flipping halfway through (45-60 seconds per side).
Transfer them to a wire rack and prop the rack up on one side so the base is on the lower side. Sprinkle with salt from a height for even coverage.
Serve immediately and enjoy!
Notes
1 quick pass through the batter is enough: A thick coat fills the gaps between the strands and the bundle stops snapping apart under your teeth. Bubbles and sound call the finish: Wait until the big bubbles turn fine and the sound goes high and light. Pulled before that, a bundle comes out oily and heavy with the middle still doughy.A gummy middle means the bundle was too thick: The outside can color while a packed bundle never dries through the center. Tear the bundles you have left in half again before they go into the batter.Never let enoki get wet: Mushrooms drink water in and hold it at the surface, which washes the dusting flour away and leaves the batter nothing to grip. Wet enoki dropped into hot oil is also the surest way to get spitting.Salt them the moment they hit the rack: Neither the enoki nor the batter is seasoned, so every bit of flavor rides on this salt. While they are hot, the thin film of oil is still moving and the crystals sink into it.