Instructions
1. Mix the flour, sugar, and salt. Knead in the shortening briefly with your hands, about 30 seconds.
2. Add the egg, ½ cup water, and the vinegar, mixing well to form a soft dough. Form the dough into a ball (see note), wrap in plastic, and chill for 1 hour.
3. Wash the sweet potatoes well and cut into large chunks. Fill a 4-quart saucepan with water, add the sweet potatoes and cinnamon sticks, and bring to a boil.
