01 - Preheat oven to 400°F. 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 cubed cold butter to dry mixture 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 combined.
05 - Pour wet ingredients into the dry and stir gently until just combined, avoiding overmixing.
06 - Gently fold fresh or frozen 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 arrange on the prepared baking sheet.
09 - Lightly brush the tops of wedges with heavy cream.
10 - Bake for 18 to 20 minutes or until golden brown. Transfer to a wire rack to cool.
11 - Whisk powdered sugar, milk or cream, and vanilla extract until smooth.
12 - Drizzle vanilla glaze over cooled scones before serving.