Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.In a medium bowl, toss together the blueberries and 1 tablespoon cornstarch. Add the honey, lemon zest, lemon juice, thyme, and vanilla. On a lightly floured surface, roll the puff pastry out into until 1/4 inch thick. Cut into 4 rectangles, placing each on the prepared baking sheet. Arrange the blueberries evenly over each rectangle, leaving a 1/2 inch border. Fold the edges up and over the blueberries. Brush the edges of the pastry with beaten egg and sprinkle with coarse sugar. Transfer to the oven and bake for 20-25 minutes or until golden brown. It is OK if the edges get dark. Let cool slightly and serve with ice cream. Enjoy!