Place the cherries, sugar and lemon juice in a saucepan over a medium heat
Simmer for 20 minutes then stir in the dissolved cornstarch

Cook until the sauce thickens, about 5 minutes
Set aside while you prep the pastry

Preheat the oven to 180 oC

Roll out until the sheet of pastry
Cut out 12 equal sized circles

Spread the cherries onto six of the pastry circles leaving about 1cm of space around the edge of the pastry, this stops the filling leaking everywhere when you bake the pastries

Brush the space you have left at the edge of the pastries with the beaten egg
Place the remaining six circles of pastry on top of the filled slices

Seal the edges by pressing down with a fork all the way round the perimeter
Place on a baking sheet lined with parchment paper

Cut a little steam hole in the middle of ech pastry
Brush the pastries with the beaten egg and sprinkle on a little extra sugar if you like

Bake in the oven for about 15 minutes or until golden brown
Serve dusted with a little icing sugar