Wash and dry chillies very well to remove all dust and dirt. Remove and discard stalks. Chop chillies finely. Separate and peel garlic cloves. Chop garlic finely.
Combine chillies, garlic, sugar and salt in a large glass jar and loosely cover. Let jar stand at room temperature for 4–5 days. Stir jar once a day with a freshly-washed clean spoon. Mixture will bubble slightly as it ferments. This is normal.
After 4–5 days, pour contents of jar into a pot. Add all remaining ingredients and bring to a simmer. Simmer for 5–6 minutes. Adjust seasoning to taste. Sauce should be hot, salty and slightly sour. Turn off heat and let sauce stand in pot until lukewarm.
Purée sauce in a blender until very fine and strain through a very clean sieve, pushing it through with a spatula. Discard residue in sieve. You should get about 350 ml (11⅔ fl oz) sauce.
Store sauce in a very clean glass jar in the refrigerator. Scoop it out only with a clean dry spoon. It will keep indefinitely. If sauce starts to change colour or develop off-flavours or off-aromas, throw it out and make a new batch.
This base sauce can be used as a table condiment or for dressing noodles and spicing up gravies and fried rice.