100g                 butter
   500g                 minced onion
   4      cloves        garlic -- pressed
   475ml                tomato ketchup
   475ml                Chili sauce
   150g                 brown sugar -- packed
   100ml                fresh lemon juice
   50ml                 red wine vinegar
   2      tablespoons   Worcestershire sauce
   1      tablespoon    prepared English mustard
   2      teaspoons     salt
   2      teaspoons     black pepper
   1      teaspoon      cayenne

Heat the butter in a large non-reactive saucepan over medium-high heat. Add the onions and garlic and sauté for 2 to 3 minutes, until just soft. Pour in the ketchup and Chili sauce, and blend in well. Add the rest of the ingredients. Bring the mixture to a boil, then reduce the heat and simmer for 30 to 45 minutes, stirring occasionally.

This sauce will keep for up to 2 weeks in an airtight jar in the refrigerator.

Begin applying the sauce warm to barbecuing brisket, about 30 minutes before the end of the cooking time.

My Notes: In place of the Chili sauce I used some fresh roasted red chillies pureed in the food processor with a little water.