Cornish-influenced savory pastries filled with meat, potatoes, and chiles are a Hidalgo mining town tradition. This protein-rich, family-friendly snack is a fresh, portable meal with British-Mexican heritage.
In a large bowl, combine the flour and salt, then cut in the cold butter with your fingers or a pastry cutter until the mixture resembles coarse crumbs.
Slowly mix in cold water until a smooth, cohesive dough forms. Wrap and chill the dough in the refrigerator for at least 30 minutes.
Meanwhile, in a medium skillet over medium-high heat, cook ground beef until browned, breaking up any clumps with a spatula. Drain excess fat.
Add onion and poblano pepper to the skillet, cooking for 3–4 minutes until softened. Stir in diced potato, oregano, cumin, and black pepper. Cook another 5 minutes, stirring occasionally.
Season the filling with salt, then remove from heat and cool to room temperature for even pastry assembly.
Preheat oven to 375°F (190°C). Divide dough into 8 portions and roll each into a 6-inch circle on a floured surface.
Place a heaping spoonful of cooled meat filling in the center of each circle, fold over to form a half-moon, and crimp edges with a fork to seal.
Beat the egg and brush it over the tops of the pastes for a golden finish.
Transfer pastes to a lined baking sheet; bake for 25–30 minutes until pastry is crisp and golden brown, rotating the pan halfway for even baking.
Cool on a wire rack briefly before serving, allowing the filling to set and avoid burns from hot steam.