Make sure before starting you have a puff pastry thawed or close to being completely thawed.
Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.
In a bowl, add blueberries, cornstarch, cane sugar, lemon zest and juice, and vanilla powder. Stir together gently. Set aside.
On a lightly floured surface, with a rolling pin roll the puff pastry out into until it measures 10x10 inches. Slice pastry in half, then each half into thirds for a total of 6 rectangles, placing each on the prepared baking sheet.
With a pairing knife, score a ¼ inch border around the outside of the pastry (this helps the pastry rise). Do not cut through the pastry but just enough to see the border.
In another small bowl, combine the dairy free milk and maple syrup. Brush gently across the rectangles. If using, sprinkle turbinado sugar evenly across the top.
Add the blueberry mixture to the inside of the scored pastry, leaving the ¼ inch scored edge open. Repeat with remaining pastries until all have an even amount.
Transfer to the oven and bake for 18-20 minutes or until golden brown.
Let cool slightly and serve and enjoy!