Finely puree the chillies, garlic, vinegar and water in a blender. Strain the puree through a sieve into a saucepan, straining the finer solids with it to give the sauce more body.
Add the remaining ingredients and bring to the boil, stirring occasionally. Reduce the heat until the sauce simmers. Let simmer, stirring occasionally, until the amount has reduced to just under a liter. If you want your sauce to be thicker, just let it cook longer. Season to taste with salt.
Let the sauce cool, fill into wide-mouth bottles or glasses. Keeps in the refrigerator for up to four weeks.