- Preheat the oven to 375°F. To prepare the pastry, combine the flour, sugar and salt. Cut in the butter until the texture of coarse meal. Add the egg yolk and water and blend just until dough comes together. Shape the dough into a disc, wrap in plastic wrap and chill for 15 minutes.
- Roll out the pastry on a lightly floured surface into a rectangle ¼-inch thick, about 20 by 12 inches. Trim edges of dough and cut into six squares. Mix the sugar with cinnamon and toss the apples to coat. Place an apple in the center of each square. Wet the edges of each pastry square and bring corners up to meet at top of apple and cinch together. Place the dumplings in an ungreased baking dish (quite close together).
- To prepare the syrup, bring water, sugar and cinnamon to a simmer for five minutes. Remove from heat and stir in butter (this can be prepared ahead of time). Pour the hot syrup over the dumplings. Bake for 45 minutes, until golden brown on top. Serve warm.