1. Prepare Dough: Stir together flour and sugar. Cut shortening into flour mixture with a pastry blender or fork until crumbly. Add buttermilk, stirring just until dry ingredients are moistened. Shape dough into a disk; wrap in plastic wrap. Chill 12 to 24 hours.
2. Meanwhile, prepare Filling: Bring apples and water to cover (about 3 1/2 cups) to a boil in a large saucepan over medium-high heat. Reduce heat to low, and simmer, stirring occasionally, 1 hour. Remove from heat; cover and let stand 1 hour.
3. Drain apples; place in a large bowl. Coarsely mash apples with 2 Tbsp. granulated sugar and next 4 ingredients. (A pastry blender does a great job.) Cover and chill 12 to 24 hours.
4. Prepare Cinnamon Sugar: Stir together 1/4 cup granulated sugar and 1 Tbsp. cinnamon.
5. Pour oil to depth of 2 inches into a Dutch oven; heat over medium-high heat to 350°. Turn dough out onto a lightly floured surface. Divide into 18 portions; shape into balls. Flatten into 3-inch circles; roll into 5-inch circles. Working with 1 circle at a time, spoon 1 Tbsp. filling into center of each circle; brush edge with water. Fold dough over filling. Press edges with a fork to seal.
6. Fry, in batches, in hot oil 3 to 4 minutes or until golden. Transfer to a paper towel-lined baking sheet. Sprinkle both sides of hot pies with cinnamon sugar.