Preheat the oven to 425F (210C).
Line two baking sheets with parchment paper and set aside.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt and grated lemon peel.
Grate the frozen butter and toss it into the flour mixture.
Use a pastry cutter or two knives to work in the butter just until the mixture resembles coarse crumbs,
Make a well in the centre and pour in one cup of buttermilk.
With a rubber spatula, gently toss together the mixture just until it appears moistened.
Turn out the dough on a floured surface.
Dust a rolling pin with flour and roll out your dough into a 16 inch square.
Scatter the blueberries over the dough.
Dust your hands with flour and start rolling the dough into a long cylinder. Use a pastry cutter to help loosen the dough from the work surface if needed.
Use a pastry cutter to help loosen the dough from the work surface if needed.
Once your dough is completely rolled out, press it slightly down to a thickness of about 1 and 1/4 inches while maintaining 16 inches in length.
Next, cut the dough into 7 equal rectangles and then cut each rectangle diagonally in half to form a triangle. (Alternately you can cut into 8 rectangle pieces and then each diagonally in half) Both work well.
Divide the triangle pieces onto the prepared baking sheets. Brush each scone with the remaining buttermilk and sprinkle generously with the coarse sugar.
Bake one sheet at a time, with the rack on the highest position, for 18 minutes or until the blueberry lemon scones are a gorgeous golden brown.
While one sheet is in the oven keep the other chilling in the fridge.
Allow the scones to cool before drizzling with the lemon glaze.
Just before serving, whisk together the icing sugar and lemon juice.
Here is where you can adapt the icing according to your taste. If you prefer a thicker lemon icing simply add more sugar.
Drizzle the scones with the lemon glaze and enjoy.