Note: To help ensure flaky crust, thoroughly chill all the crust ingredients and the mixing bowl and pastry blender at least 30 minutes before starting.
In chilled mixing bowl, sift together flour, and salt. Using a pastry blender, cut in the butter and shortening until the mixture resembles coarse sand. Add ice cold water a tablespoon at a time, mixing after each addition, until the dough holds together. Knead the dough just enough to form into a ball. Wrap in plastic wrap and chill for 15 minutes.
Preheat the oven to 400 F. Generously butter a 9x13-inch baking dish.
In a small bowl, stir together the brown sugar, cinnamon, and nutmeg. Add softened butter and mix to combine.
On a lightly floured surface, roll the chilled crust into a large rectangle, about 24x16 inches. Cut the dough in to 6 even pieces. Place each apple into the center of one of the crust pieces with the opening facing up. Divide the butter mixture between the apple, pushing some into the core area.
Bring the edges of the dough piece up and over the filled apple. Pinch the edges together, encasing the apple in the dough piece. Moisten fingers slightly to help the edges seal together. Repeat process with all of the apples. Place the enclosed apples in the prepared baking dish.
In a sauce pan, combine water, sugar, vanilla and butter. Place over medium heat, and heat to a boil. Reduce heat, and allow to boil for 5 minutes or until sugar has dissolved.
Carefully, pour sugar syrup mixture over dumplings in baking dish. Bake dumplings in preheated oven for 50 to 60 minutes, until crust is golden brown and a knife will slide into the apple easily. Makes 6 dumplings.