Add the cherries and sugar to a medium saucepan over medium-low heat.
In a small bowl, stir the lemon juice with the cornstarh so no lumps remain.
Occasionally stir the cherry mixture for about 10 minutes, until it starts to bubble and thicken a little.
Add the cornstarch slurry to the cherry mixture while continuously stirring. Bring the cherries back to a boil. Once it boils, stir in the vanilla and salt and pour into a medium bowl. (When you taste it, there should be no chalky cornstarch taste remaining if brought to a true boil.)
Let the mixture cool completely or cover and put in the fridge for a day or two.
When you're ready to make the pies, remove the puff pastry from the freezer and lay each sheet on parchment to thaw. Cover with a clean towel or plastic wrap.
While you wait, make the egg wash by whisking the egg with a tablepoon of milk. Grab a pastry brush and cookie cutters if using. (A knife can be used to make steam vents too.)
Once the pastry is not frozen hard but still quite cold, cut the pastry into the size pieces you will use. (I cut my rectangle puff pastry sheets into squares to place one on top of the other.
When the pastry is pliable, still very cold though, place about two tablespoons of the cherry compote in the middle of the dough. When all are done, use the pastry brush to brush the edges with the egg wash. This will act like glue to keep the top layer attached. (Be careful not to brush the sides of the edges or they won't rise much.
Next, cut your desired small shape, into the top pieces of dough and carefully place that over the piece with the compote and egg wash.
Using a fork, push down on the edges of the dough to crimp the top and bottom layers together.
Carefully brush the tops of the dough with a little more egg wash and sprinkle the sugar over each pie. When complete, place into the fridge to cool for about 15 minutes while you preheat the oven to 190C/ 375F.
Bake the hand pies for about 25-30 minutes until golden brown, puffed up, and no wet spots remain on the bottoms. Let cool a few minutes before enjoying.
*If you use fresh cherries or other fruit, use about 2 1/2 cups.
*Cinnamon, ground ginger or another spice would work nicely in place of the vanilla.
* If you decide not to use a cookie cutter on the tops of the pies, make an x with a pairing knife for the steam vent.