In a medium-sized bowl, combine all pork meatball ingredients and mix continuously in one direction (clockwise or anti-clockwise) with a pair of chopsticks or a fork. About 2 - 3 minutes.
In a large skillet or non-stick pan, add cooking oil and bring the pan up to medium-low heat then form bite-sized meatballs with your hands, adding them into the pan as each is formed. (note 3) Brown and caramelise both sides of meatballs then remove and set aside. Meatballs do not have to be cooked at this point.
Depending on the size of your pan, you may need to do this in two batches.
Turn the heat off and in the same pan (no need to wash), add dark soy sauce, rice wine vinegar, brown sugar and sesame oil. Turn the heat back on to low heat and bring the sauce up to a low simmer. About 1 minute.
Add meatballs back into the pan and gently coat with sauce with a spoon or flipping them.
Mix cornstarch with cold water until cornstarch has disolved, pour into the pan. Mix the sauce with a wooden spoon until the sauce is thick and glossy.
Serve once meatballs are cooked, sprinkle with spring onions and/or sesame seeds.