Prepare the Pie Dough (Crust):

1. Mix Dry Ingredients: In a large mixing bowl, combine the flour, salt, and sugar.

2. Cut in the Butter: Add the cold, cubed butter to the dry ingredients. Using a pastry cutter, fork, or your hands, work the butter into the flour mixture until the texture resembles coarse crumbs with pea-sized butter bits.

3. Add Ice Water: Gradually add the ice water, one tablespoon at a time, mixing with a fork until the dough begins to come together. You may need to add a little extra water if the dough is too dry.

4. Chill the Dough: Turn the dough onto a lightly floured surface and knead it a few times until it forms a ball. Split the dough in half, shape each half into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes. Chilling the dough helps ensure a flaky texture when baked.

Prepare the Blueberry Filling:

5. Cook the Blueberries: In a medium saucepan, combine the blueberries, sugar, lemon juice, cinnamon (if using), and salt. Cook over medium heat, stirring occasionally, until the blueberries release their juices and begin to break down (about 5-7 minutes).

6. Thicken the Filling: In a small bowl, mix the cornstarch with a little water to form a slurry. Add the slurry to the blueberry mixture and stir well. Continue cooking for another 2-3 minutes, until the mixture thickens. Remove from heat and stir in the vanilla extract. Let the filling cool while you roll out the dough.

Assemble the Hand Pies:

7. Roll Out the Dough: Take one disk of dough out of the fridge and place it on a lightly floured surface. Roll it out to about 1/8-inch thickness. Using a round cutter or a small bowl, cut out circles of dough (about 4-5 inches in diameter). Repeat with the second disk of dough.

8. Add the Filling: Spoon a heaping tablespoon of the blueberry filling into the center of each dough circle.

9. Seal the Pies: Fold the dough over the filling to form a half-moon shape. Press the edges together tightly, then crimp the edges with a fork to seal.

10. Apply the Egg Wash: If desired, brush the tops of the hand pies with a beaten egg wash (egg and water mixture) for a golden, glossy finish.

Bake the Hand Pies:

11. Preheat the Oven: Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper.

12. Bake the Pies: Arrange the hand pies on the prepared baking sheet and bake for 30-35 minutes or until golden brown and the crust is flaky. Keep an eye on them to avoid over-baking.

13. Cool: Allow the hand pies to cool on a wire rack for a few minutes before serving.

Cut and Serve:

14. Serve Warm or Cold: These hand pies are delicious both warm and at room temperature. You can serve them on their own or with a scoop of vanilla ice cream or a dollop of whipped cream for an extra indulgence.