01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together all-purpose flour, granulated sugar, baking powder, baking soda, salt, and lemon zest.
03 - Add cold, cubed butter to dry ingredients. Use a pastry blender or fingertips to cut in butter until mixture resembles coarse crumbs.
04 - In a separate bowl, whisk together heavy cream, egg, and vanilla extract.
05 - Pour wet mixture into dry ingredients. Stir gently until just combined, taking care not to overmix.
06 - Gently fold fresh or frozen blueberries into the dough using a spatula.
07 - Turn dough onto a lightly floured surface. Pat into a 7-inch round circle about 3/4 inch thick.
08 - Cut the dough into 8 equal wedges. Transfer wedges to the prepared baking sheet.
09 - Lightly brush the tops of each wedge with additional heavy cream.
10 - Bake for 18 to 20 minutes, or until scones turn golden brown. Remove and cool on a wire rack.
11 - Whisk together sifted powdered sugar, milk or cream, and vanilla extract until smooth. Drizzle the glaze over cooled scones.