Divide the filling evenly among the puff pastry squares (about 4-5 cherries per turnover).
Using a pastry brush, brush egg wash on the edges of each puff pastry square.
Gently fold each pastry into a triangle, covering all of the filling.
Use a fork to crimp the edges of each turnover. Then, cut a slit in the center of each turnover.
Gently transfer the turnovers to the baking sheet, spacing them evenly apart. (If using two baking sheets, do four and four turnovers on each.)
Brush the tops of each turnover with egg wash and sprinkle with coarse sugar, if desired.
Bake for 18-20 minutes, or until puffed and golden brown.
Allow to cool at least 5-10 minutes before serving. Dust with powdered sugar, if desired.
Store leftovers in an airtight container at room temperature or in the fridge.