Place the sliced chicken breast in a large bowl. Add the soy sauce, salt, and black pepper. Stir well to ensure the chicken is evenly coated in the seasoning. Set aside while preparing the batter.

In a separate large mixing bowl, combine the all-purpose flour, cornstarch, and baking soda. Create a well in the center of the dry ingredients. Add the whisked egg and cold soda water into the well. Gently mix until the batter is just combined. It is acceptable for the mixture to remain slightly lumpy.

In a deep skillet, wok, or Dutch oven, pour the vegetable oil to a depth suitable for shallow frying. Heat the oil over medium heat until it reaches approximately 350°F (175°C). If a drop of batter sizzles immediately upon contact, the oil is ready.

Dip each strip of seasoned chicken into the batter, ensuring it is fully coated. Allow any excess batter to drip off before carefully placing each piece into the hot oil. Fry in batches to avoid overcrowding the pan.

Fry the chicken pieces for 2–3 minutes on each side, or until the coating is golden brown and the chicken is fully cooked through. Use a slotted spoon to transfer the chicken to a paper towel–lined plate to drain excess oil.

Serve the Chicken Tempura hot, accompanied by a dipping sauce of choice or as part of a larger meal.