How to Make It
Preheat the oven to 350°. Using a lightly floured rolling pin, roll out the puff pastry on parchment paper to a 14-by-12-inch rectangle and cut into eight 3-by-3 1/2-inch pieces. Transfer the parchment paper to a baking sheet.
In a medium bowl, toss the cherries with the sugar, cornstarch, lemon juice and cinnamon. Brush the pastry edges of the rectangles with the beaten egg wash. Mound the filling in the center of each pastry and fold the dough over; press to seal and crimp decoratively. Brush the pies with beaten egg and make a small slit in the top of each one. Bake for 40 minutes, until golden.