Preheat oven to 400°F. Line a large baking sheet with parchment paper; set aside.
In a large bowl mix together flours, salt, baking powder, baking soda, sugar, and lemon zest.
Cut the butter into small cubes then quickly work it into the mixture (using your fingers) until it resembles a coarse meal.
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.
Add in the blueberries and gently fold them into dough with a spatula - don’t worry if some of the berries break up a bit.
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 and carefully transfer to the prepared sheet.
Lightly brush each scone with the egg wash, then sprinkle the top of each scone with sugar.
Bake for 18-20 minutes, or until the tops are lightly golden brown.
Cool for about 10 minutes, then make your glaze.
In a small bowl whisk together the lemon juice and confectioners sugar. Drizzle over warm scones and serve at once.