Blueberry Sauce

Mix blueberries and sugar in a large non-reactive bowl. Mash berries with a potato masher a little bit to help them release some juice and leave them overnight.

Sterilize jars.

Take some of the lemon juice and place it in a small bowl. Add cornstarch and mix well until you have a paste.

Place berries in a larger pan, add lemon juice and zest and bring everything to a boil. As soon as it starts to boil, add the cornstarch paste and mix very well to avoid clumps. Lower heat and let cook for about 10 minutes.

Pour sauce into sterilized jars, leaving 1 cm (0.4 inches) headspace. Place lids on the jars and leave to cool. Store in the cellar or a dark, cool place.