Start by chilling 175 ml water and 60 ml carbonated water (preferably unopened) in the refrigerator. Measure 95 g cake flour and 30 g cornstarch into a bowl and chill in the freezer for 30 minutes.
In the meantime, wash, dry, and cut your vegetables according to the ingredients list.
Once your batter ingredients are thoroughly chilled, start heating your cooking oil to 170 °C (338 °F) to 180 °C (356 °F). While it's heating, pour the water and sparkling water into a bowl, then add 15 ml rice vinegar and 3 ice cubes.
Pour the cake flour, cornstarch and ½ tsp baking powder into a sifter, then sift it into the water one-third at a time, gently mixing by drawing crosses with chopsticks.
The batter is ready once there is no more dry flour. Be careful not to overmix, tempura batter should be a bit lumpy (not smooth).
Once your oil is hot, dust your ingredients with cake flour and dip them in the batter before placing them straight into the oil.
Cook each type of ingredient in separate batches for even cooking. Most vegetables take 2-3 minutes, root vegetables will take 2-4 depending on thickness. Leaves (like perilla) and nori will take about 30 seconds.
Once light and crispy, transfer to a wire rack to drain the excess oil.
Take a small bowl and sift in ½ tsp matcha powder. Add ½ tbsp salt and mix well to make the matcha salt for dipping.