In a large bowl, stir shortening and water until shortening is melted. Gradually stir in flour and salt until a very soft dough is formed; cover and refrigerate for 1-1/2 hours.
Quarter and thinly slice potatoes; place in a large bowl with onions, beef, and seasonings.
Divide dough into 12 equal portions (~132g per ball).
On a floured surface, roll out 1 portion at a time into a 10-in. circle. Mound 2 cups filling on half of each circle; dot with 1 teaspoon butter. Moisten edges with water; carefully fold dough over filling and press edges with a fork or braid to seal.
Preheat oven to 425°. You will reduce to 350° after 15 min.
Place on ungreased baking sheets. Cut several slits in top of pasties. If desired, brush with cream or beaten egg.
Bake at 450° for 15 minutes
Reduce heat to 350°
Bake at 350° until golden brown, about 1 hour. Cool on wire racks. Serve hot or cold. Store in the refrigerator.
