Heat the oven to 400°F (200°C) and line a baking sheet with parchment paper.

Whisk the flour, granulated sugar, baking powder, and salt together in a large bowl.

Grate the very cold or frozen butter into the flour mixture, or cut it in with a pastry cutter, until coarse crumbs form.

In a separate bowl, whisk together the heavy cream, egg, and vanilla extract.

Pour the wet mixture into the dry mixture and stir just until the dough begins to come together. Fold in the blueberries gently, taking care not to crush them.

Transfer the dough to a lightly floured surface and shape it into a roughly 8-inch round about 1 inch thick. Cut the round into 8 wedges.

Place the wedges on the prepared baking sheet and chill them for about 15 minutes if the dough has softened.

Bake for 20–25 minutes, until the tops are lightly golden and the centers are set. Frozen blueberries may require a few additional minutes.

Cool the scones before glazing. Whisk the confectioners' sugar with enough lemon juice to make a thick but pourable glaze, then drizzle it over the cooled scones.