1. Keep batter and liquids very cold for a crisp coating. Do not overmix the tempura batter or it will turn dense. Use sparkling water for lighter crunch. Maintain oil temperature around 350 F for best texture and to prevent greasiness. For air fryer use 400 F and spray with oil then cook 10 to 12 minutes turning once but crust will be less airy. Substitute gluten free flour blend for flour and potato starch for cornstarch if needed