Make the dough:
Whisk together flour, granulated sugar, baking powder, and salt. With your fingers, rub in the butter until the dough looks like coarse cornmeal.
Gradually add water over flour mixture, one tablespoon at a time. Use a fork to stir until a dough forms. In the bowl form a flat circle. Cover with cling film and refrigerate for 1 hour, at least.
In a small pot, combine pumpkin puree, brown sugar, spices and salt. Bring to a simmer over medium heat; reduce heat to medium-low and simmer, stirring and scraping bottom of pot so that it won't burn, 5 to 7 minutes, until the filling has thickened. Cool completely.
Preheat oven to 375° F. Line 2 baking sheets with parchment. Roll out dough on a floured surface to 1/8" thick. Use a 4" round cutter and cut out rounds. Reroll and cut again in order to yield 16 - 18 empanadas.
Spoon one generous tablespoon of pumpkin filling in the center of each round. Add 1/2 teaspoon shaved chocolate on top of the filling. Fold over half of the round to form a half-circle shape; seal or crimp edges with a fork or with your fingers, as desired. Arrange empanadas on prepared sheets and refrigerate for 15 minutes.
In a small bowl, whisk the beaten egg and the 1 tbsp of water; brush over each empanada, then turn and brush bottom with egg wash. Sprinkle empanadas with the brown sugar on one side.
Bake the empanadas until they have turned golden brown and are firm to the touch, 20 to 25 minutes. Let them cool down about 5 minutes before serving. Enjoy!
