In a large bowl, combine the flour and salt. Add the chilled, cubed butter and mix with your fingers or a pastry cutter until the mixture resembles coarse crumbs.

Add the cold water and vinegar to the flour mixture. Mix until the dough comes together, then form into a ball. Wrap in plastic wrap and refrigerate for 30 minutes.

While the dough chills, heat olive oil in a skillet over medium heat. Add the onion and garlic, cooking until softened, about 3-4 minutes.

Add the ground beef to the skillet and cook until browned, breaking it up with a spatula. Mix in paprika, cumin, chili powder, salt, and pepper.

Stir in the tomato paste, chopped green olives, and hard-boiled egg. Cook for an additional 2 minutes, then remove from heat and allow the filling to cool completely.

Preheat the oven to 375°F (190°C). Roll out the dough on a lightly floured surface to about 1/8-inch thickness. Cut into circles using a 4-5 inch round cutter.

Place a spoonful of the cooled filling in the center of each dough circle. Fold the dough over to form a half-moon shape, pressing the edges together. Seal by crimping with a fork or twisting the edges.

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

Bake in the preheated oven for 20-25 minutes, or until golden brown. Serve warm and enjoy!