Step 1

Stem and halve 100g of chillies, place in the bowl of a food processor. Stem, halve and deseed the remaining 400g chillies. Coarsely chop and place in the food processor. Add garlic and 250ml white vinegar. Process until finely chopped.

Step 2

Place the chilli mixture, remaining vinegar and caster sugar in a large saucepan over a low heat. Cook, stirring, for 5 minutes or until the sugar dissolves.

Step 3

Increase heat to high and bring to the boil. Reduce heat to medium and simmer, stirring occasionally, for 35-40 minutes or until the sauce thickens. Pour into sterilised airtight bottles and seal.