In a large mixing bowl, whisk together the flour and salt.

Add the cold, diced butter to the flour mixture. Using a pastry cutter or your fingers, work the butter into the flour until the mixture resembles coarse crumbs.

In a small bowl, beat the egg and combine it with the cold water and vinegar.

Gradually add the liquid mixture to the flour mixture, stirring with a fork until the dough starts to come together.

Turn the dough out onto a lightly floured surface and knead gently until it forms a smooth ball. Do not overwork the dough.

Wrap the dough in plastic wrap and refrigerate for at least 30 minutes before using.

After chilling, roll out the dough on a floured surface to your desired thickness and cut into circles for empanadas.