Gluten-Free Blueberry Turnovers

Method

1. To make the crust: In a large bowl, whisk together the gluten-free flour, sugar, xanthan gum, and salt.
2. Cut the cold butter into small pieces and work them into the flour mixture using a pastry blender or your fingers until the mixture resembles coarse crumbs with some pea-sized butter pieces remaining.
3. In a separate bowl, whisk the eggs and lemon juice (or vinegar) together until very foamy. Add this to the dry ingredients and stir until the dough holds together. If needed, add a little cold water, a tablespoon at a time, until the dough comes together.
4. Divide the dough in half, shape each half into a flattened rectangle, wrap tightly in plastic wrap, and refrigerate for at least 1 hour, or up to overnight.
5. Let the dough sit at room temperature for 10 to 15 minutes before rolling it out.
6. To make the filling: If using fresh blueberries, rinse and drain them. Place the blueberries in a saucepan. In a small bowl, whisk together the sugar, gluten-free flour, and salt. Add this mixture to the blueberries along with the lemon juice and stir to combine. Cook over medium heat, stirring occasionally, until the mixture thickens, about 5 minutes. Remove from heat and let cool to room temperature.
7. Preheat the oven to 425°F and place a rack in the middle. Line a baking sheet with parchment paper.
8. On a lightly floured surface (use gluten-free flour), roll each piece of dough into a 7x17.5-inch rectangle. Using a sharp knife or pastry wheel, cut each rectangle into ten 3.5-inch squares.
9. Place a heaping tablespoon of the blueberry filling in the center of 10 of the squares. Brush the edges of these squares with some of the beaten egg.
10. Cut a small vent (e.g., a slit or decorative shape) in the center of each of the remaining 10 squares.
11. Place a vented square on top of each filled square, aligning the edges. Press the edges together with a fork or a pie crimper to seal.
12. Brush the tops of the pies with the remaining beaten egg and sprinkle with coarse sparkling sugar, if using. Transfer the pies to the prepared baking sheet.
13. Bake for 18 to 20 minutes, until golden brown. Remove from the oven and let cool on the baking sheet for 20 minutes before serving.