01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, salt, and lemon zest.
03 - Add cold butter cubes and cut in using a pastry blender or fingertips until mixture resembles coarse crumbs.
04 - In a separate bowl, whisk heavy cream, egg, and vanilla extract until blended.
05 - Pour wet ingredients into dry mixture and stir gently until just combined without overmixing.
06 - Gently fold blueberries into the dough using a spatula.
07 - Turn dough onto a lightly floured surface and pat into a 7-inch circle about 3/4 inch thick.
08 - Cut dough into 8 wedges and transfer to the prepared baking sheet.
09 - Lightly brush scone tops with heavy cream.
10 - Bake 18 to 20 minutes until golden brown, then cool on a wire rack.
11 - Whisk powdered sugar, milk or cream, and vanilla extract until smooth.
12 - Drizzle glaze over cooled scones before serving.