Place the minced pork, ginger, garlic, spring onions, chilli, chopped herbs, egg, salt and kecap manis in a bowl and mix well with your fingers.
Divide the mixture into 20 portions and roll each into a ball.
Spread the sesame seeds evenly over a large plate. Roll the meatballs in the seeds to coat.
Heat 1 tablespoon of the oil in a large nonstick wok or frying pan over a medium heat, add the meatballs and fry, turning frequently, for 12–15 minutes until browned and cooked through. Transfer to a plate with a slotted spoon and keep warm.
Wipe the pan clean with kitchen paper, add the remaining oil and heat over a medium-high heat. Add the choi sum stalks and stir-fry for about 1–2 minutes until just wilted. Stir in the noodles and stir-fry for 3 minutes, or until piping hot.
Mix together the soy sauce and sweet chilli sauce and add to the pan with the choi sum leaves and meatballs. Toss together until heated through, then serve immediately in warmed bowls, garnished with spring onion, diced red chilli and coriander leaves.