To make the batter…In a bowl, combine flour and salt. Scoop 1/3 cup of the mixture and transfer the 2/3 cup to the fridge until needed.
When ready to fry, pour in a little at a time of ice-cold carbonated water into the 2/3 cup flour, stir until combined between each addition.
To make Tempura…About every ¼-inch, make a few shallow cuts along the inside of the prawns, making sure to not cut too far.
Flip the shrimp over, belly side down, and gently push down on each cut with fingers – should hear each muscle breaking under pressure.
Rinse under cold water and pat dry. Transfer the prepared prawns onto a plate lined with more paper towels and transfer to the fridge until needed.
When ready to fry, bring the oil temperature to 375ºF.
Working with one at a time, dip ingredient (either veggie or prawn) in the reserved 1/3 cup flour, shaking off any excess, and dip it in the batter. Place on a plate before looking after another ingredient.
Working in batches of 4 to 6 at the most, carefully drop in the hot oil, making sure they don’t stick together, and fry them accordingly until golden brown.
Scoop them up and transfer onto a wire rack for a couple minutes to remove any excess oil. Serve immediately with Tempura Dipping Sauce (Tentsuyu)