Combine the flour and salt in a large bowl, mixing well to ensure an even distribution.

Add the cold butter to the flour mixture, using your fingers or a pastry cutter.

Gradually pour in the cold water, mixing until the dough just comes together.

Knead the dough briefly on a floured surface until smooth, then wrap it in plastic wrap and refrigerate for at least 30 minutes.

Heat a small amount of oil in a large skillet over medium heat.

Sauté the onion, garlic, and bell pepper (if using) for about 5 minutes until softened.

Incorporate the ground beef (or chicken) into the skillet, cooking until browned.

Mix in the chopped olives and hard-boiled egg (if using). Cook for another minute, then remove from heat and let the filling cool completely.

Roll out the chilled dough on a floured surface to about 1/8 inch thick.

Spoon about a tablespoon of the cooled filling onto the center of each circle.

Fold the dough over forming a half-moon shape and press the edges to seal tightly.

For baking, preheat your oven to 400°F (200°C) and bake for 20-25 minutes until golden brown.

For frying, heat oil in a deep skillet and fry the empanadas until golden and crispy, about 3-4 minutes per side.

Garnish with freshly chopped parsley and serve warm.