•  In a large bowl, whisk together the flour, baking powder, salt, lemon zest, and sugar. 
• With a pastry blender or two forks, cut in the cold cubed butter until pea-sized pieces remain.
• Pour half of the heavy cream in slowly, gently mixing until the dough is moistened. Add the blueberries and remaining cream. Again, gently mixing just until moistened and incorporated. Remove the dough from the bowl and place it on a lightly floured surface. 
• Gently knead the dough until it comes together and shape into a flattened disk.
• With a bench scraper portion the dough into 8 wedges. Place the wedges of dough onto a parchment-lined baking sheet.
• Refrigerate the scones for at least 30 minutes. 
• While the scones are chilling, preheat the oven to 400°F. 
• In a small bowl, whisk together the egg and tablespoon of heavy cream. Brush the egg wash onto each scone, you will not use all of the egg wash.
• Bake the scones for 20 - 25 minutes, or until golden brown.

Make the Icing

• Once the scones have cooled, make the icing. Pour the lemon juice into the sifted powdered sugar. Whisk the mixture until thickened and incorporated. Drizzle the icing over the cooled scones.