Step 1: In a large bowl, whisk the flour and salt. Cut in the chilled butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs.
Step 2: Beat one egg with the cold water and gradually add it to the flour mixture. Mix until a dough forms. Knead lightly on a floured surface for 2 minutes, wrap in plastic, and refrigerate for 30 minutes.
Step 3: In a large skillet over medium heat, brown the ground beef. Once cooked, remove the beef and set aside, leaving the fat in the pan.
Step 4: Add the chopped onions to the skillet and sauté until translucent and soft, about 10 minutes. Stir in the garlic, cumin, and smoked paprika, cooking for another minute until fragrant.
Step 5: Return the beef to the pan and mix thoroughly with the onions and spices. Stir in the chopped olives. Remove from heat and let the filling cool completely in the refrigerator.
Step 6: Preheat your oven to 400°F (200°C). Roll out the dough on a floured surface to about 1/8-inch thickness. Use a 5-inch round cutter to cut out circles.
Step 7: Place 2 tablespoons of the cold beef filling in the center of each dough circle. Fold the dough over to create a half-moon shape and press the edges firmly to seal.
Step 8: Create a decorative edge by twisting and folding the rim (the repulgue) or by pressing with the tines of a fork.
Step 9: Place the empanadas on a parchment-lined baking sheet. Brush the tops with the egg wash for a golden finish.
Step 10: Bake for 20-25 minutes or until the pastry is golden brown and crisp. Allow to cool for 5 minutes before serving.