Prepare the Dough

• In a large bowl, combine the flour and salt. Add the chilled butter and cut it into the flour using a pastry cutter or fork until the mixture resembles coarse crumbs.
• Beat the egg with the cold water, then add it to the flour mixture. Stir until the dough begins to come together. Knead briefly to form a smooth dough, then wrap in plastic wrap and refrigerate for 30 minutes.

Make the Filling

• Heat olive oil in a skillet over medium heat. Add the chopped onion and garlic, cooking until softened, about 5 minutes.
• Stir in the shredded chicken, tomato sauce, olives, cumin, paprika, salt, and pepper. Cook for an additional 5 minutes until the mixture is well combined and heated through. Set aside to cool slightly.

Assemble the Empanadas

• Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.
• Roll out the chilled dough on a lightly floured surface to about ⅛-inch thickness. Cut out circles using a 4- or 5-inch round cutter.
• Place a spoonful of the chicken filling in the center of each dough circle. Fold the dough over to form a half-moon shape, and press the edges together to seal. Use a fork to crimp the edges.

Apply the Egg Wash

• Brush the tops of the empanadas with the beaten egg for a golden finish.

Bake the Empanadas

• Arrange the empanadas on the prepared baking sheet and bake in the preheated oven for 20-25 minutes, or until golden brown.

Cool and Serve

• Allow the empanadas to cool slightly before serving.