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

Add cold butter cubes and use a pastry cutter or fingers to mix until the texture resembles coarse crumbs.

Gradually add cold water, mixing until a dough forms.

Shape into a ball, wrap in plastic wrap, and refrigerate for 30 minutes.

Heat olive oil in a pan over medium heat. Add onions and garlic and sauté until soft.

Stir in shredded chicken, cumin, smoked paprika, black pepper, salt, and tomato paste. Cook for 2-3 minutes until well combined.

Remove from heat and mix in shredded cheese and cilantro. Let the filling cool.

Preheat oven to 375°F (190°C).

Roll out the chilled dough on a floured surface to 1/8-inch thickness.

Use a round cutter (about 3 inches in diameter) to cut out small circles.

Place a spoonful of chicken filling in the center of each dough circle.

Fold the dough over to form a half-moon shape and press the edges to seal. Use a fork to crimp the edges.

Arrange empanadas on a parchment-lined baking sheet.

Brush the tops with egg yolk for a golden finish.

Bake for 20-25 minutes until golden brown and crispy.

(Alternatively, fry empanadas in hot oil at 350°F (175°C) for 2-3 minutes per side until crispy and golden.)

Let the empanadas cool slightly before serving.

Serve warm with salsa, sour cream, or guacamole for dipping.