Tip all the ingredients except the sugar into a mini chopper or blender and blend to a chunky sauce. Scrape the contents into a shallow saucepan with the sugar and 100ml water and bring to a simmer.

Simmer for 15 mins, stirring occasionally until it becomes syrupy. Keeping a close eye on it, continue to simmer and stir for 5 mins more until it easily coats the back of the spoon and you see the bottom of the pan when you stir. Leave to cool and infuse for 1-2 hours. Will keep in a small sterilised jar for up to a month.