Lightly and randomly score the surface of the pork all over (to tenderize) and cut into 2 cm cubes. Add 1/2 t salt, some white pepper, 1 T cornflour, 1 egg white and 1/2 t sesame oil (optional) and mix well (using your hands to mix better) and leave 1/2 hour. Note: add 1/2 t 5-spice powder if like.
Cut all the veg into 1 1/2 cm cubes/slices. Mix all the sauce ingredients together, stirring well to dissolve the sugar. Taste and season it if necessary.
Heat 2 to 3 cups of oil until very hot. Coat each piece of pork with cornflour and drop into oil in 3 batches. Move the pork around so they don't stick together. Fry until light to medium brown and very crispy, and drain on paper towels. Place pork on serving plate.
Pour the oil away leaving about 1 T in the wok and add all the veg into the same wok (there'll be enough oil coating the wok but in restaurants, oil is added so the sauce will have a sheen). Fry until veg are half-done. Now add the sauce ingredients (give it a stir before adding into wok) and stir until sauce thickens. Pour the sauce over the pork, or you can add the pork in and then dish out.