Bring a pot of water to a boil and add the oxtails in. Let it come to a boil again and drain the contents. Clean the pot, fill it back up with 3L (12.7 US cup) water and bring the water back to a boil.
While that's happening, wash the oxtails to remove any impurities. As soon as the pot starts boiling again, put the cleaned oxtail cutlets back in.
Add the sate sauce, sugar, chicken bouillon powder and salt. When it starts to bubble, turn the heat down to low for a slow simmer. Let it cook on low heat for 1 hour.
Peel and chop the daikon into large chunks, roughly 10cm (4") wide. Put it in the pot and simmer with the other ingredients for 2 hours.
Cut the scallions into 5cm (2") segments and put them in the pot to simmer for 15 minutes.
Meanwhile, bring a large pot of water to a boil and cook the rice noodles for 5 minutes or until al dente. Drain and run under cold water, the let it drip dry in a colander until ready to eat.
To make the sauce, start by heating up the oil in a saucepan over medium heat. Add the garlic in to brown for 30 seconds.
Pour the chopped onions in and let them cook for 1 minute.
Add 10 tbsp of the sate sauce in and season with the sugar. Mix well, then let it simmer on low heat for 2 minutes. Transfer to a bowl for later.
To serve, bring the soup up to a boil and add the greens and noodles in to eat as you go.
Dip the oxtails in the sauce and enjoy as is!