Keep 2-3 clean jars handy.
1. Slice a small cross into the tops and bottoms of the tomatoes, then put the tomatoes in a large bowl or dish and cover with hot water. Leave to stand for 20 minutes, drain and remove the skins. Cut off the stem side of each tomato, then roughly chop the tomatoes.
2. Heat the oil in a deep saucepan or pot and stir-fry the onion over medium heat for 10 minutes until soft. Add the garlic, chillies and bay leaves, then stir-fry for another 5 minutes.