Put the oil in a large, heavy-based pot on a medium-high heat. Cook half the pork in a single layer, turning occasionally, for eight to 10 minutes, until golden brown all over, then transfer to a bowl and repeat with the remaining pork.
Add the onion to the pot once the 2nd batch of pork has been removed and cook for eight to 10 minutes, until the onion has softened. Add the garlic, ginger and chillies and cook for another 3 minutes.
Add all the remaining ingredients apart from the spring onions, bring to a boil, the turn down to a simmer, cover and cook for an hour and 20 minutes, until the pork is tender.
Remove the lid, cook for a further 10-15 minutes, until the sauce has thickened, then take off the heat. Garnish with the spring onions and serve with steamed rice and vegetables.