Preheat oven to 400.  Adjust baking rack to the middle-low position.

LIne a large baking sheet with parchment paper or a silicone baking mat.

In a large bowl, whisk the flour, sugar, baking powder, salt, and lemon zest.

Grate the frozen butter and toss into the flour mixture.  Combine it with a pastry cutter, a fork, or your fingers until the mixture resembles coarse meal.

In a small bowl, whisk the cream, egg, and vanilla together.

Drizzle it over the flour mixture and then toss the mixture together with a rubber spatula until everything appears moistened.  

Slowly and gently fold in the blueberries.  Try your best not to overwork the dough at any point.  (I've found my dough to be a little dry, making it challenging to incorporate the blueberries, but do your best.)

Work the dough into a ball with floured hands and transfer to a floured surface.

Press into an 8" disk and cut into 8 equal wedges with a very sharp knife, a pizza cutter, or any other cutting tool.  (I sometimes cut it into more pieces to make smaller scones.)

Place scones at least 2" apart on the prepared baking sheet.

Bake for 20-25 minutes or until lightly golden and cooked through.  

Remove from the oven and allow to cool for a few minutes.

To make the glaze, whisk together the powdered sugar and 2 T. of the lemon juice until smooth.  Add more juice if needed to think it out.

Drizzle the glaze over the scones right before serving. However, they keep well so you can add the glaze as soon as you'd like.