In a bowl, mix together blueberries, sugar, lemon juice, corn starch, and salt. Mix until there is not more dry corn starch.
In a medium heat pan melt butter then add the blueberries.
Stir for 5 minutes, we just want to create a thick sauce base around the blueberries. Making sure not to break the blueberries either.
Set it aside in the fridge to cool.
Roll out your puff pastry sheets into a 10x10 inch square.
Cut into 5 strips that are 2.5 inches in thickness.
Place 2 tbsp of the blueberry filling onto the puff pastry sheet.
Brush the sides with a light layer of eggwash.
Fold over the other half of the puff pastry sheet.
Using a fork, seal the edges.
Cut off the excess pastry to make it look clean.
Brush the top of the pie with more eggwash.
Deep fry at 350F until golden brown about 8 minutes.