Combine flour, salt, and sugar in a food processor and pulse briefly to incorporate.

Add chilled butter cubes and pulse until the mixture resembles coarse crumbs with pea-sized pieces remaining.

Slowly stream in ice water while pulsing until the dough begins to mass; do not overwork.

Divide dough into two equal discs, wrap in plastic, and refrigerate for 60 minutes to hydrate the flour.

In a small bowl, whisk blueberry preserves with cornstarch to ensure filling stability during baking.

Preheat oven to 375°F (190°C) and line a baking sheet with parchment paper.

Roll out the first dough disc to a 1/8-inch thickness and cut into eight 3x4 inch rectangles.

Repeat the rolling and cutting process with the second dough disc.

Arrange eight rectangles on the baking sheet and brush the perimeter of each with an egg wash made from the egg and heavy cream.

Deposit 1.5 tablespoons of the blueberry mixture into the center of each rectangle.

Place the remaining eight rectangles on top, pressing edges with a fork to create a mechanical seal.

Prick the surface of each tart three times with a fork to allow steam to escape.

Bake for 22 to 25 minutes or until the crust reaches a light golden-brown hue.

Transfer to a wire rack and cool completely.

Whisk powdered sugar, milk, vanilla, and blueberry juice until smooth, then spread over the cooled pastries.