Cut 450 g chicken breast into stick-like pieces about 3-4cm thick (approx 1½ inches) and pierce each piece thoroughly all over with a fork.
Cut each stick into large bitesize pieces, cutting at an angle to increase the surface area of each piece.
Place the chicken into a bowl and crack in 1 egg. Mix well until the egg yolks and whites have combined and the chicken is coated.
Add 3 tbsp sake, ½ tsp sugar, ½ tbsp grated ginger root, ½ tbsp grated garlic, 1 tsp salt and 1 tsp toasted sesame oil and mix well.
Add 3 tbsp tapioca starch of mix until combined. Then cover the mixture with plastic wrap and marinate in the refrigerator for 30 minutes.
Start heating your cooking oil to 160 °C (320 °F). While you wait, add 8 tbsp tapioca starch, 2 tbsp lemon juice and ½ tbsp lemon zest to a container and mix with a fork. Scrunch the mixture in your palms to make small clumps of starch.
Roll each piece of chicken generously in the starch mixture, pressing it down to secure. When the oil is hot enough, add the coated chicken and fry for 3 minutes for the first fry.
Transfer to a wire rack and rest for 3-5 minutes, the chicken will continue to cook in the residual heat. If you're cooking in multiple batches, you can use this time to cook the next batch.
Increase the heat of the oil to 180 °C (356 °F). Once heated, add the chicken once more, this time frying for 1 minute or until crispy and golden.
Transfer to a wire rack, this time to drain the excess oil.