In a large bowl, combine the flour and salt. Cut in the butter until the mixture resembles coarse crumbs.

Stir in the cold water, a tablespoon at a time, until the dough comes together. Wrap in plastic wrap and refrigerate for 30 minutes.

In a skillet over medium heat, add olive oil and sauté the onion until translucent, about 5 minutes. Add garlic and cook for an additional minute.

Stir in the shredded chicken, diced potatoes, cumin, paprika, salt, and pepper. Cook for 3-4 minutes until heated through. Remove from heat and let cool.

Preheat the oven to 400°F (200°C).

On a lightly floured surface, roll out the dough to about 1/8 inch thick. Cut into 4-inch circles.

Place a tablespoon of the chicken filling in the center of each dough circle. Fold over and press the edges to seal, crimping with a fork if desired.

Place the empanadas on a baking sheet lined with parchment paper. Brush the tops with the beaten egg.

Bake for 25-30 minutes or until golden brown. Let cool slightly before serving.