The bones of this sauce is below, however you must feel free to make this for your own palate, if you like it hot then add more curry powder.  Also, different brands of tomatoes have slightly different acidity so you may need a little more sugar.  Leftover chakalaka is really lovely on toast with a fried egg 

Ingredients
2 tbsps oil 
250g onions, finely chopped 
1-2 tbsp curry powder
1 x (400g crushed tomatoes 
400mls water (use the empty tomato tin to pick up all of the tomato juice) 
2 tbsp Mrs Balls chutney 
1 chicken stock pot
1 tbsp Worcestershire sauce
1 tbsp home made peri peri sauce 
1 tsp sugar 
½ tsp ground black pepper

Method
Heat the oil in a large saucepan over a medium heat and fry the onion for 5-7 minutes until soft and translucent - you don't want any colour on the onions.

Add the curry powder and cook for a minute. Add the rest of the ingredients and stir again then reduce the heat a little and leave to cook for 45-60 minutes until thick, stirring from time to time.

Check the balance and seasoning, you may need to add a little more sugar or salt.