1. Cut chicken into cubes and marinate with soy sauce, white pepper powder, egg and minced garlic. Set aside and let it marinate while you prepare the sauce.
2. For the lemon sauce, mix everything together except for corn flour slurry. Set aside.
3. Spread potato flour out on a flat tray and pour in marinated chicken (including all the liquid). Generously coat chicken pieces with flour and squeeze it slightly just to get the craggy bits of flour to stick to the chicken.
4. Fry chicken in hot oil until golden brown.
5. Using another pan, pour in pre-mixed lemon sauce and bring to a simmer. Slowly pour in corn flour slurry and stir until thickened. Adjust sweet and sour flavour with sugar and lemon juice as needed.
6. Add in fried chicken into the thickened lemon sauce and mix quickly to combine. Serve!