Pastry:

In a large bowl, sieve the flour, sugar, and salt. Add the cold cubed butter and use your hands to crumble it into the dry ingredients. (The mixture should resemble coarse sand, or breadcrumbs).

In a small bowl, whisk together the egg, water, and vanilla bean paste. Add to the flour mixture, and use a bench scraper to mix until just combined, then use your hands to knead gently until a soft dough forms.

Flatten dough into a disc, wrap in clingfilm/plastic wrap, and transfer to the refrigerator to chill while you prepare the blueberry jam.

Blueberry Jam:

In a small saucepan, combine blueberries and sugar. Simmer over medium heat until berries have broken down, mixture has thickened, and temperature reaches 106° C / 225° F on a candy thermometer. Alternately, you can do a manual test to see if jam stage has been reached (see notes above). Remove from heat, stir in lemon juice and zest, then transfer jam to the fridge to cool while rolling your pastry.

Assembly:

Preheat oven to 190° C / 375° F. Line a baking tray with parchment or a silicone baking mat.

Remove your disc of chilled pastry from the refrigerator. On a rolling mat or lightly floured countertop, use a rolling pin to roll pastry to approximately 3 millimeters / 1/8 inch thickness.

Using a sharp knife, cut the pastry into 6 x 9 centimeter / 2.5 x 3.5 inch rectangles. (If preferred, you can also use a large biscuit cutter to cut your pastry into squares or circles instead.) Re-roll the scraps and cut into additional rectangles.**

Transfer half of the rectangles to prepared baking tray. Spoon a small amount of blueberry jam into the middle of each rectangle, allowing a wide border of pastry on all sides. (It will be tempting to add extra jam, but try to stick with just a teaspoonful—overfilled pastries will be difficult to seal and will leak in the oven!)

With a pastry brush, lightly egg wash the borders, then top each pastry with a second rectangle.*** Use your fingers to gently press down around all edges, sealing the jam inside the pastry.

Egg wash the tops of the pastries. Dip a fork in the egg wash, and use it to crimp the edges.

Use a sharp knife to cut a small vent in the top of each pastry, or prick the tops with a fork.

Transfer tray of pastries to the freezer and freeze for 10 minutes prior to baking.

Bake pastries in preheated oven for 20-25 minutes, or until pastry is flaky and golden brown. Remove from oven and transfer to a wire rack to cool completely.

Vanilla Bean Glaze:

While pastries cool, prepare the vanilla bean glaze by whisking all ingredients together in a small mixing bowl. If desired, add a bit more milk or cream to adjust the consistency—less liquid will produce a thicker, more icing-like result; more liquid will create a semi-transparent glaze.

When pastries are completely cool, place wire rack over a rimmed tray or a sheet of parchment. Use a teaspoon to drizzle the glaze over each pastry, then top with sprinkles or sanding sugar.

Blueberry hand pies are best enjoyed within two days. Unglazed pies will also freeze well.