01 - Cut the chicken breasts into thin strips measuring 1/2 x 2 inches. Pat thoroughly dry with paper towels and season evenly with salt and pepper.
02 - In a mixing bowl, whisk together the all-purpose flour, cornstarch, and baking powder until fully combined.
03 - Lightly beat the egg in a separate bowl, then mix with the ice-cold sparkling water.
04 - Pour the wet mixture into the dry ingredients. Stir briefly with chopsticks or a fork, leaving the batter slightly lumpy. Do not overmix to maintain crispiness.
05 - Heat the vegetable oil in a deep pan or fryer to 350°F.
06 - Dip the seasoned chicken strips into the batter, allowing excess to drip off, then carefully add to the hot oil.
07 - Fry in batches for 3 to 4 minutes until golden and crisp, turning once halfway through. Avoid overcrowding the pan to maintain proper oil temperature.
08 - Transfer cooked chicken to a wire rack or paper towel-lined plate to drain excess oil.
09 - Combine soy sauce, mirin, rice vinegar, sugar, and grated ginger in a small saucepan. Heat gently while stirring until the sugar completely dissolves, then cool to room temperature.
10 - Arrange the chicken tempura on a serving platter and serve hot with the dipping sauce on the side.