In a large bowl, combine the flour and salt, then rub in the cold butter with your fingertips until the mixture resembles coarse crumbs with a few pea-size pieces remaining.
Drizzle in the cold water, tossing with a fork until the dough starts to clump, then gently bring it together with your hands, form into a disc, wrap, and chill for about 30 minutes.
Meanwhile, heat the oil or butter in a skillet over medium heat, add the chopped onion and grated carrot, and cook until softened but not browned.
Add the ground beef to the pan, breaking it up with a spoon, and cook until no longer pink, then stir in the salt, black pepper, and nutmeg or allspice.
Sprinkle the tablespoon of flour and the Worcestershire sauce over the mixture, cook for another minute, then remove from the heat and let the filling cool completely.
Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.
On a lightly floured surface, roll out the chilled pastry to about 1/8 inch thickness and cut out circles about 6–7 inches wide using a bowl or small plate.
Place a generous spoonful of the cooled beef filling on one half of each pastry circle, leaving a border around the edge.
Fold the other half of the pastry over the filling to make a half-moon shape, press the edges together firmly, and crimp with a fork or your fingers to seal.
Arrange the bridies on the prepared baking sheet, brush the tops with the egg wash, and cut a small slit or two in each for steam to escape.
Bake for 25–30 minutes, or until the pastry is puffed and deep golden, then let the bridies cool for at least 10 minutes before serving.