Gather tempura ingredients: all-purpose flour, cornstarch, ice-cold water, egg, vegetables or seafood, and oil for frying
Chill the flour, water, and bowl before mixing
Heat oil in a deep pot to 340–350°F
Beat the egg lightly with ice-cold water
Add flour and cornstarch to the liquid
Mix gently until just combined
Leave the batter slightly lumpy
Coat vegetables or seafood lightly in flour if desired
Dip ingredients into the batter
Fry in small batches until light golden and crisp
Remove with a slotted spoon or spider
Drain on a wire rack or paper towels
Serve immediately with dipping sauce if desired