Combine chicken breast pieces with soy sauce in a bowl. Cover and marinate in the refrigerator for half an hour.
In a separate bowl, beat the egg with cornstarch, season with some salt and black pepper. Add the marinated chicken pieces to the batter.
Deep-fry chicken pieces until brown. Drain on paper towels and set aside.
Combine sugar, chicken broth, lemon juice, salt and turmeric (if using) mix until well combined.
Bring to a boil, lower heat and add slurry (for thicker sauce, add more cornstarch-water mixture) Pour the sauce over the chicken and mix.
Serve with rice and veggies on the side.