Chop the onions and fry them gently until they caramelise:
Then add the chillies and the ginger. Only fry for a short time as the chillies start releasing their heat and you don't want it all to escape. You will find yourself choking like crazy at this point.
Then add the tinned tomatoes, salt and sugar. Put the lid on the pot and just let it simmer away for about half an hour.
I then use a stick blender to puree everything first, but you may prefer the 'rustic' version.
The sauce is now done. You can now divide it into portions and freeze it.
If you want to keep the sauce in jars, this is where the hassle starts. This is without doubt, a real faff, but absolutely essential for preservation. Wash the jars, then put them on a baking tray in the oven at around 130° C for at least 10 minutes. This kills off any bacteria and the jars are hot (this is also important).
The lids should be put into a bowl of boiling water for about 10 minutes too. I have tried putting them in the oven with the jars but this hardens the rubber seal on the lid and ruins it.
The golden rule of jarring is 'hot into hot'. Never put hot sauce into a cold jar or vice-versa. This will cause the glass to shatter. Get yourself organised here as you need to get it all done as quickly as possible before everything cools down. I use a wide base jam funnel to cleanly scoop the sauce into the jar, then screw the lid on immediately. Remember, everything is still pretty hot so be careful not to burn yourself.
Once the jars are full just leave them to cool. You will see the lid contract as this happens and, if you use those fancy 'clicky' lids, you will hear a very satisfying click as the sauce-preserving vacuum is reached.
That's pretty much it. As you see, the hardest bit is jarring so if you are happy to just freeze it, then it makes the job a lot easier.
You can experiment with many other ingredients. Fruit seems to be popular at the moment: grapefruit, mango or raspberries for example. I used to also add mint leaves to mine, that gives a nice little after taste too.
Let me know how you all get on, and how you experimented and improvised.
Spread the sauce!