01 - Cut the chicken breasts into thin strips measuring approximately 1/2 x 2 inches. Pat dry thoroughly 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 well combined.
03 - In a separate bowl, lightly beat the egg, then mix it with the ice-cold sparkling water. Keep this mixture chilled.
04 - Pour the wet mixture into the dry ingredients. Stir very briefly with chopsticks or a fork, leaving the batter slightly lumpy. Do not overmix to maintain the light, crispy texture.
05 - Heat the vegetable oil in a deep pan or fryer to 350°F. Use a thermometer to ensure proper temperature.
06 - Dip the seasoned chicken strips into the batter, allowing any excess to drip off.
07 - Carefully add the battered chicken to the hot oil. Fry in batches for 3 to 4 minutes until golden and crisp, turning once. Do not overcrowd the pan to maintain oil temperature.
08 - Transfer cooked chicken to a wire rack or paper towels to drain excess oil.
09 - Combine soy sauce, mirin, rice vinegar, sugar, and grated ginger in a small saucepan. Heat gently over low heat until the sugar completely dissolves, then remove from heat and cool to room temperature.
10 - Arrange the chicken tempura on a serving plate and serve immediately with the dipping sauce on the side.