Place flour and salt in the bowl for a food processor. Pulse 2 - 3 times to combine
Add chilled butter and pulse 8 - 12 times until mixture is consistency of coarse sand
Add the egg and vinegar and turn the food processor to 'on'
Slowly pour cold water through feed tube just until a dough ball forms
Remove dough from work bowl and divide in half
Form each half into a 5" - 6" disk and wrap in plastic wrap. Place in the refrigerator for at least 30 minutes, and up to 2 days.
Remove a disk from the refrigerator and divide into 4 equal portions. Return 3 portions to the refrigerator and work with just one portion at a time
Take a portion of dough and and roll it into a small ball
Place the ball on a lightly floured work surface and press to flatten
Using a rolling pin, roll the dough out to approximately 8" circle
Using a plate or template, use a sharp knife to cut the dough into a circle creating an empanada shell
Place the empanada shell on a piece of parchment paper or waxed paper and set aside
Repeat rolling and cutting process with the remainder of the dough
Working with one empanada shell at a time, place between a ¼ cup and a ½ cup filling slightly off center of the empanada shell. Leave between ½ inch and ¾ inch along the edge without any filling
Gently lift one edge of the empanada shell and carry it over the filling bringing it down to meet the opposite edge of the shell. You should form a semi circle
Starting at one end of the semi circle, make a series of small folds around the edge to join the two halves of dough and to seal the empanada
When all the empanadas are full, place them on a parchment lined baking sheet and place in the refrigerator to chill for 30 minutes.
While the empanadas are chilling, preheat the oven to 400°F
Remove the empanadas from the refrigerator. Brush them with an egg wash if you would like to help with the color while baking
Bake the empanada for 15 to 20 minutes, until empanadas are golden brown
Remove from the oven and let cool briefly. Serve warm, or store in the refrigerator for up to a week.