- Wash blueberries and add them to a cold heavy bottomed pot on the stove. For a smoother syrup, mash some or all of the blueberries with a fork.
- Add cold water, lemon juice, and sugar to the pan. The amount of sugar in this recipe is completely up to taste, so be conservative in the beginning because sugar can always be added later.
- If using lemon strips, then add to pot now
- Turn heat up to medium-low and bring mixture to a simmer, stirring occasionally. Blueberries will break down naturally, but feel free to crush the berries some more for
- Once mixture has been brought to a boil, lower the heat to a simmer. Taste for sweetness level and add more sugar or lemon juice accordingly
- In a separate bowl, combine cornstarch with equal parts water and stir thoroughly until now chunks remain, then add cornstarch slurry to the simmering pot. Cornstarch added to hit liquids will clump so this is an important step
- Stir mixture occasionally to prevent burning on the bottom and sides and allow mixture to thicken to desired consistency. Keep in mind that the syrup will also be slightly thicker once it had cooled down
- Take the pot off the heat and allow it to cool until warm
- Add vanilla extract now and stir in
- If using lemon zest, add in now and stir
- If using lemon peel, optionally fish the strips out of the mixture with a fork
- Allow to cool completely in pot or transfer the syrup to an heat proof, air tight container and allow to cool before covering and refrigerating
- Optionally strain mixture through a mesh sieve for a completely smooth sauce
- Keep in the refrigerator for up to a week, or 3 months if sealed properly. Use as the perfect refreshing topping or add-in!