1Remove green stems from chillies, chop chillies coarsely with their seeds. Process chilli until finely chopped.
2Combine vinegar, water, sugar and salt in large saucepan. Stir over low heat, without boiling, until sugar dissolves. Add chilli, boil, uncovered, 20 mins.
3Add garlic; boil, uncovered, about 20 mins or until mixture is reduced to 3 cups (750 ml). The sauce will thicken on cooling. Stand sauce 10 mins.
4Pour hot sauce into hot sterilised bottles, seal immediately. Cool, refrigerate.