Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

Add the very cold, cubed butter to the dry ingredients. Using a pastry blender, two knives, or your fingertips, cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining.

In a separate small bowl, lightly whisk the beaten egg, 1/2 cup cold heavy cream, and lemon zest. Pour this wet mixture into the flour and butter mixture.

Gently mix with a wooden spoon or your hands until just combined and a shaggy dough forms. Do not overmix. Carefully fold in the fresh blueberries until evenly distributed.

Turn the dough out onto a lightly floured surface. Gently pat the dough into a round disc, about 7-8 inches in diameter and 1 to 1.5 inches thick.

Using a sharp knife or a bench scraper, cut the disc into 8 wedges. Carefully transfer the wedges to the prepared baking sheet, spacing them slightly apart.

Brush the tops of the scones with the remaining 1-2 tablespoons of heavy cream. This helps them achieve a golden-brown crust.

Bake for 18-22 minutes, or until the tops are golden brown and a wooden skewer inserted into the center comes out clean.

Remove from the oven and let cool on the baking sheet for a few minutes before transferring to a wire rack.

While the scones are cooling, prepare the lemon glaze. In a small bowl, whisk together the powdered sugar and 2 tablespoons of fresh lemon juice until smooth. If the glaze is too thick, add a little more lemon juice, 1/2 teaspoon at a time, until it reaches a drizzly consistency. If it's too thin, add a bit more powdered sugar.

Drizzle the lemon glaze generously over the warm (but not hot) scones. Allow the glaze to set slightly before serving.