Grease and line a cookie sheet with parchment paper.
Add the zest and sugar to a large bowl and rub it together with your fingers to release its oils.
Add the flours, baking powder and salt to the bowl and whisk them together with the sugar.
Using a pastry knife or a cheese grater, cut the butter into the flour until you have pea-sized bits of butter.
Whisk the heavy cream, egg and vanilla in a small bowl with a fork.
Add the wet ingredients and with a rubber spatula stir the dough until it’s almost coming together. Using your hands, shape it into a ball.
Add the blueberries and with your fingers, gently mix them in (avoid pressing any less you burst them).
Onto a floured surface, halve the dough and shape it into two smaller disks about 1 ½ inch thick - flattening the top slightly. Cut the circles into fourths, and then eighths so that you have 8 small triangles from both circles (so 16).
Alternatively shape it into a long rectangle (12 x 8") and slice it into 8 squares.
Set the scones on the cookie sheet, just a bit apart. The closeness helps them rise higher.
Set the pan in the freezer and let the scones freeze for at least 10 minutes.
Preheat the oven to 425 F.
Brush the scones with heavy cream and bake them for 12-15 minutes, until the bottoms are just golden.
Once they are cool, whisk the glaze ingredients together and spoon it onto the scones.