In a spacious mixing bowl, combine all-purpose flour and chilled butter, blending until the mixture resembles coarse breadcrumbs. Gradually add iced cold water, mixing until a soft dough forms. Knead lightly on a floured surface just until smooth. Wrap in plastic wrap and refrigerate for at least 30 minutes.

In a large skillet over medium heat, brown your beef until nicely seared, about 5-7 minutes. Stir in chopped onions, cooking until they become translucent. Add peeled and diced potatoes and rutabaga, stirring well. Season with Worcestershire sauce, salt, pepper, and fresh herbs. Allow the filling to cool to room temperature.

On a lightly floured surface, roll out the chilled dough to about 1/8-inch thickness. Using a large round cutter, cut out circles about 6 inches in diameter. Spoon a generous amount of the cooled beef filling onto half of each circle, leaving space around the edges. Fold the dough over to seal, crimping the edges with your fingers or a fork.

Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper. Place the prepared pasties on the baking sheet, brush the tops lightly with beaten egg, then bake for 30-35 minutes, watching for a deep golden brown color.

Once baked, remove the pasties from the oven and let them rest on a wire rack for 5-10 minutes. Serve warm and enjoy.