Japanese tempura is defined by its ethereally light, lacy batter and precise oil temperature control. The batter is deliberately undermixed — lumps and streaks of dry flour are correct, not a mistake. Ice-cold sparkling water, minimal mixing, and screaming hot oil produce the characteristic crisp, almost transparent coating that shatters on first bite. Portuguese missionaries introduced the frying technique to Japan in the 16th century; Japanese cooks refined it into something entirely different and more precise.
Batter: ice-cold sparkling water, egg yolk, cake flour (low protein). Mix with chopsticks in 3-4 strokes — lumps of dry flour must remain. The batter should be thin enough that the ingredient is visible through it. Oil temperature: 170-180°C for vegetables, 180-190°C for seafood. Small batches only — no more than 30% of the oil surface covered at once. Ingredients must be completely dry before dipping. The lacy 'flowers' of batter that form around the edges are the signature — flick extra batter off your chopsticks into the oil near the piece for more lacework.
Keep the batter bowl sitting in a larger bowl of ice to maintain cold temperature throughout frying. For the lightest tempura: add a tablespoon of vodka to the batter — alcohol evaporates faster than water, creating extra-crispy coating. Dip vegetables halfway — the exposed surface provides contrast. Tentsuyu dipping sauce: dashi, mirin, soy sauce (8:2:2 ratio) with grated daikon and ginger. Drain on a wire rack, never paper towels — paper traps steam.
Over-mixing the batter — gluten develops and the coating becomes heavy and bready. Using warm water — cold inhibits gluten formation. Oil not hot enough — greasy, heavy result. Too many pieces at once — temperature drops. Not drying ingredients. Using all-purpose flour — too much protein. Preparing batter in advance — it should be made immediately before frying.