In a large bowl, whisk together the flour and salt.
Cut in the butter using a pastry cutter or your hands until the mixture resembles coarse crumbs.
In a separate small bowl, whisk together the egg, water, and vinegar.
Slowly pour the wet mixture into the flour mixture, stirring until the dough starts to come together.
Knead the dough on a floured surface for a few minutes until smooth.
Wrap the dough in plastic wrap and refrigerate for at least 30 minutes before using.
Roll out the dough and cut into circles for empanadas, then fill and bake or fry as desired.