Using the large holes of a box grater, grate the frozen butter over a plate, and then refreeze the butter to keep it firm.
Measure and add the flour, sugar, baking powder, salt, and all but ½ tablespoon of lemon zest to a large bowl and whisk to combine.
Cut the frozen grated butter into the flour and the butter is broken down.
Mix the milk, egg and, 2 tablespoons of lemon juice, together and add to the flour mixture and stir with a fork until just combined and the dough looks shaggy.
Turn the dough onto a floured surface and knead a couple of times to bring the dough together.
Gently roll the dough into a 12 x 12 rectangle. Then fold one-third of the dough over, then the over third to create a long rectangle, like an envelope. Now fold that rectangle in half so you have a very small rectangle. Chill this dough for 15 minutes.
Preheat the oven to 425° F. and line a baking sheet with parchment paper or a Silpat.
Place the chilled dough back on the floured surface and reroll the dough to a 12 x 12" rectangle. It is easier to do this if you take the rolling pin and gently press down on the dough in several spots to flatten it a bit for your start rolling.
Sprinkle the blueberries over the dough then roll the dough over the berries like a cinnamon roll. Now you have a 12" long roll. Next with the rolling pin or your hands, press down on the roll to flatten it and it will be about 4" wide and should still be about 12" long.
Cut the dough on the diagonal to create 8 triangles and place on a parchment-lined baking sheet.
Bake at 425 degrees for 15 - 18 minutes until the scones are baked through and brown.
While the scones are cooling make the glaze by mixing the powdered sugar, milk and remaining zested lemon peel to a smooth consistency.
When scones are cooled drizzle the glaze over the top.
These scones will keep for several days in an airtight container.