Put the blueberries with the 200 g water, sugar and vanilla extract in a small saucepan and bring to the boil. As soon as the mixture boils, reduce the temperature and let everything simmer for another 6 minutes.
Now stir the cornstarch with the rest of the water until smooth and as soon as the blueberries have finished cooking, add the starch-water mixture to the blueberries. Stir everything until smooth and briefly put on the stove again until the starch has set. The sauce should be a little thicker, then it`s perfect. Have fun cooking at home.