Put all the ingredients in a pot and crush the berries with a potato masher.

Bring the mixture to a boil over medium-high heat then reduce the heat to medium and simmer for about 30 minutes, stirring occasionally until the liquid has reduced and the mixture has thickened.

Put a fine mesh strainer over a large bowl and pour the blueberry mixture into the strainer. Gently press on the solids with a spatula to extract all of the syrup. Discard the solids.

Allow the syrup to cool completely, then store in the refrigerator for up to a week.