The longest part is waiting for the blueberries to cool. Instructions. On a lightly floured surface, roll each sheet of the thawed On a lightly floured surface, roll the puff pastry (it should still be cold) into a 10-inch square. Place croissant pieces in a 9 inch square pan. Sprinkle with blueberries. Beat cream cheese, sugar, eggs and vanilla in medium bowl with electric mixer until well blended. Preheat the oven to 425F. Such an easy dessert recipe, these blueberry puff pastries can be made pretty quickly. Preheat oven to 350 degrees. So while the blueberries are cooling, pop the pastry shells in the oven. In a small bowl, stir together the blueberries, sugar, cornstarch, lemon juice, cinnamon and a pinch of salt.