Pound the chicken breast with a meat tenderizer to thin out. Cut into roughly 1 inch wide and 3 inch long strips.
Mix the black pepper, salt, soy sauce, ginger, and garlic in a small bowl. Pour into zip-loc bag or airtight container and add chicken. Marinate for 15 minutes. Meanwhile, make the tempura batter.
Fill a large bowl with ice and water, then place a medium bowl in it. Add 1 egg to the medium bowl and whisk well.
Sift the ⅓ cup cake flour and ⅓ cup cornstarch into the bowl with the egg.
Gradually add in the ⅓ cup cold water and mix everything until just combined and a batter forms.
Add the chicken pieces to the bowl a few at a time and coat well with the batter.
Heat oil to 350ºF (180°C) in a medium-sized pot (or deep fryer).
Add in only 2-3 pieces of battered chicken at a time. Fry until crispy on the outside, about 2 minutes on each side.