Add the blueberries and water to a saucepan and heat over low heat for 10 mins. Whil simmering, gently mash the blueberries with a potato masher to help release the juice.
Strain the juice and discard the blueberry remains.
Add the strained blueberry juice back into the saucepan with the sugar.
Bring to the boil over medium-high heat until it thickens enough to coat the back of a spoon.
Add the lemon juice and stir over medium-heat for 1 minute.
Remove from heat and stir through the vanilla extract.
Nutritional information is an estimate and provided as a courtesy. The values may vary according to the ingredients and tools that are used. Please use your preferred nutritional calculator for more detailed information.