Set rack to the center position of the oven. Preheat to 400°F. Line a large baking sheet with parchment paper and set aside.
In a large bowl mix flours, salt, baking powder, baking soda, sugar, and lemon zest.
Grate cold butter or cut butter into small cubes then quickly work it into the flour mixture using your fingers until a coarse meal is achieved. Gently fold in the blueberries with a spatula.
In a small bowl, whisk together the egg, Greek yogurt, milk, and vanilla, then add to flour and butter mixture. Use a fork to stir everything together until just moistened.
Pour the shaggy dough out onto a clean floured work surface and shape the dough into an 8-inch circle. Cut the dough into 8 wedges. Lightly press in more blueberries on top of each scone of desired. Carefully transfer to the lined baking sheet.
Whisk together egg and milk in a small bowl. Lightly brush each scone with the egg wash. Bake for 15-16 minutes, or until the tops are lightly golden brown.
Cool for about 5 minutes, then transfer to a cooling rack.
For the lemon glaze, whisk together confectioners sugar, lemon juice and yogurt in a small bowl. Add more sugar or juice if needed for a thicker or thinner consistency.
Drizzle the glaze over warm scones and sprinkle with lemon zest if desired. Best served immediately or within a few hours.
Store in an airtight container for up to one day.
If the scone dough feels dry and does not come together right away when shaped, add more milk to the dough, 1 teaspoon at a time until it forms a circle when pressed together.