Heat the oil in a medium sized sauce pan. Add the onion and cook on low-medium for 5 mins - until the onion is soft. Give it a stir every minute or so. Add in the ginger and garlic and cook for a further minute. Add in the rest of the ingredients, turn up the heat and bring to a gentle bubble. Turn the heat back down to medium and allow everything to bubble gently for 20 minutes. Give it a stir every so often.
After 20 minutes, turn off the heat and blend the mixture in the pan using a hand blender. I like to give it just a few pulses so the sauce still has some texture.
Prep ahead: You can allow the sauce to cool and then cover and refrigerate for up to a week. Reheat in a pan before serving..Nutritional Information is per cup.