For the dough:
For the filling:
For the filling: put the blueberries in a small pan, heat over medium heat and crush them slightly so they release their juice. Stir frequently for 5 minutes.
Mix the cornstarch with some cold water and dissolve. Add to the blueberry mixture to make it thick. Allow to cool and set aside.
For the dough: put the butter and sugar in a bowl and beat for 2 minutes until obtaining a creamy mixture. Add the egg yolk and vanilla extract and beat at low speed for 30 seconds. Add a third of the flour and beat at low speed, repeat this procedure with the other two thirds of flour. Finish bringing the dough together with your hands and, using a rolling pin, roll out each dough potion until obtaining two sheets around 4 mm thick. Refrigerate for 3 hours.
Preheat the oven to 360°F.
Using a very sharp knife, cut the previously refrigerated dough sheets into the shape of a pumpkin (it is important that they all look the same). Then make triangle-shaped eyes and Halloween-type mouths on half of the pumpkins.
With a spoon, spread the blueberry mixture on the center of each pumpkin dough (faceless). Put the corresponding pumpkins on top of each base and close the edges with a fork.
Smear beaten egg over each pumpkin with a cooking brush. Put all the cookies in the oven for 20 minutes until brown and allow to cool.
