Place your cubed butter, flour and salt in a mixing bowl and blend together using your finger tips until it is coarse and lumpy. Set Aside.
In a separate bowl, beat egg, water and vinegar. Add to flour mixture and combine with fork until just incorporated.
Turn out dough onto a floured surface and knead gently for a few moments. Shape dough into a rectangle. Wrap tightly in plastic wrap and chill in fridge for 1 hour or more.
When you are ready to use your dough, cut into 8 equal pieces. Using a rolling pin, roll out all 8 pieces of dough into circles. Place your filling into one side of your circle and fold over the other side to bring edges together. Using a fork, seal the open edge of your empanada. I typically will bake my empanadas for about 15 minutes at 400 degrees.