Add all ingredients to a blender and blitz until fully combined and smooth.
Pour into a saucepan and place over a low heat. Bring to a gentle simmer.
Cook for approximately 1 hour, stirring every 10–15 minutes, until the mixture has reduced by half and is thick and syrupy.
Remove from the heat and leave to cool completely.
Pour into a sterilised jar or airtight container and refrigerate. Keeps for up to 7 days.
