Chinese takeaway style sweet and sour sauce.
1. In a small pan, combine the tomato ketchup, white vinegar, water, soy sauce, white sugar and brown sugar. On a low-medium heat, bring the mixture to boiling point, stirring frequently. Once the mixture is boiling, allow to simmer for 1-2 minutes.
2. In a separate bowl, combine 1 1/2 tablespoons of cornflour and 30ml of water. Mix thoroughly and add to the simmering pan. Continue stirring frequently and simmer for a further 2-3 minutes. Remove the pan from the heat and pour the sweet and sour sauce into a serving bowl or tub.