Slice chicken into shreds
Marinate chicken with 1 tsp light soy sauce, ½ tsp sugar and 1 tsp corn starch. Mix well, add 1 tsp oil and mix again. Set aside
Slice ½ an onion into thin wedges. Set aside You may want to cut the other half into square pieces for the white sauce at this time
Slice tomatoes into bite-size wedges. Set aside
Combine 3 tbsp tomato paste, 3 tbsp ketchup, 1 tbsp white vinegar, 1 tbsp light soy sauce and 2 tsp sugar in a container. Mix well and set aside
Combine 1 tbsp corn starch with 2 tbsp water and set aside You may want to prepare another slurry for the white sauce at this time
In a pan or wok, heat on medium-high heat and add 2 tbsp oil
Add chicken. Arrange in single layer and let it cook for approx. 1 minute
Flip the chicken over and cook for approx. 45 seconds
Stir-fry to loosen chicken and remove from heat, leaving the oil chicken does not need to be cooked through at this time
Add onions and cook for 1 minute
Add prepared tomato paste mixture. Combine with onions
Add chicken back in
Add 250ml chicken stock and cover with lid. Bring to a boil
Stir the slurry and slowly pour into the sauce while mixing
Mix until sauce thickens
Taste test and make adjustments if necessary
Add tomatoes
Cover with lid and cook on low heat for 10 minutes