01 - Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
02 - Whisk together the flour, sugar, baking powder, salt, and lemon zest in a large bowl.
03 - Cut the cold, cubed butter into the dry ingredients using a pastry cutter or fingertips until the mixture resembles coarse crumbs.
04 - Whisk the cream, egg, and vanilla extract in a small bowl until combined; pour over the dry mixture and gently stir until just incorporated.
05 - Carefully fold in the blueberries, avoiding excessive mixing to maintain their shape.
06 - Turn the dough onto a lightly floured surface and pat into a 1-inch thick circle.
07 - Cut the dough into 8 wedges and place them spaced slightly apart on the prepared baking sheet.
08 - Lightly brush the tops of the scones with extra heavy cream.
09 - Bake for 18 to 22 minutes until the scones are golden and cooked through; cool on a wire rack.
10 - Whisk confectioners sugar, milk or cream, and vanilla extract until smooth; drizzle over cooled scones.