1. To make the pastry, combine the flour, salt, baking powder and curry powder in a large mixing bowl. Cut the butter into small pieces and add to the bowl. Working quickly and using your fingertips, squeeze the flour mixture and butter together and toss it by scooping under the mixture with both hands. When the mixture resembles a very coarse meal, add the water to the bowl.
2. With floured hands, mix and squeeze the dough just until it forms a ball. Knead it once or twice to combine it fully (the less kneading, the better). Separate the dough into 2 pieces, flattening each into a thick pancake; wrap the pieces in plastic, and set them in the refrigerator to chill for at least 15 minutes. (The dough will keep in the refrigerator up to 5 days. Remove it from the refrigerator 30 minutes before using it.)
3. For the filling, heat the oil in a large skillet over medium heat. Add the garlic and onion, stirring constantly for 30 seconds. Add the curry powder and cook for 2 minutes, continuing to stir and scrape the bottom of the pan. (Do not burn!)
4. Add the pumpkin and 3/4 cup of the water and blend it well with the curry mixture. Cover the skillet and reduce the heat to low. Simmer gently for 10 to 15 minutes, or until the pumpkin is soft enough to mash.
Meanwhile, in a pot, add the cabbage and enough water to cover. Bring to a boil over high heat and cook for 3 minutes. Drain completely and set aside.
5. Crush the pumpkin until smooth, add the remaining 3/4 cup water and stir. Add the cabbage, potato, carrot, chocho, Scotch bonnet pepper, salt and black pepper. Cover and simmer for 10 minutes. Remove the vegetable mixture from the skillet and place in a bowl. Let it cool. (It can be made ahead and will keep in the refrigerator, covered, for up to 5 days.) Remove the Scotch bonnet pepper before using.
6. Preheat the oven to 400°F. Cut each piece of the dough into 9 pieces. Using a rolling pin on a floured surface, roll out each piece of pastry into a rectangle shape with rounded edges. Spread a large spoonful of the cooled vegetable mixture over one side of the dough, leaving at least a 1/2-inch border on the outside edge. Using your finger, paint water around the border. Fold the other side of the dough over, and roll and crimp the edges. Lightly press a floured fork around the edge of the patty.
7. Place onto a cookie sheet and repeat the procedure with the remaining dough. (The patties may be covered in plastic and frozen at this point for later use.) Brush each patty with the egg wash and bake for 20 minutes, or until the patties begin to turn a golden color.