- Make the filling: Heat oil in a large skillet. Add onions and garlic, stirring frequently. Cook until translucent. Add curry powder. Add diced sweet potatoes, stir, and cook for about 20 minutes. Add ginger, salt and pepper to taste. Let cool completely before assembling pastries. This filling can be made 3 days in advance.
- Make the pies: Whisk egg with 1 tablespoon water to make an egg wash. Roll out dough into a large square. Cut even squares from dough, about 3 inches by 3 inches. Place 2 tablespoons of filling in center of each square. Brush egg wash around border of dough and fold over filling into a triangle.
- Preheat oven to 375 degrees. Place pastries on a parchment-lined sheet tray. Brush each with egg wash, sprinkle a generous amount of sesame seeds, then make a small cut on the top of each pastry to vent while baking. Bake until golden brown, about 25 to 30 minutes. Cool slightly before serving.