Preheat oven to 425° F (220° C). Position rack in the center of the oven.
Prepare a cookie sheet lined with parchment paper. Set aside.
Place ⅓ cup of butter in the freezer.
In a large bowl, whisk together flour, cornmeal, sugars, baking powder, salt and baking soda. Set aside.
In a small bowl, whisk together buttermilk, egg and lemon zest. Set aside.
In another small bowl, toss the blueberries with the cornstarch. Set aside.
Using the large holes of a cheese grater, grate the frozen butter over dry ingredients.
Gently but quickly toss together to incorporate the butter. Use your fingertips to rub the flour and butter together for about 1 minute. The mixture should look like coarse meal.
Gently add in the blueberries.
Make a well and pour in the liquid ingredients.
Stir gently until just combined.
Transfer to a parchment-lined baking sheet and with lightly floured hands, pat the dough together and form it into a ball. Be gentle as to not crush the blueberries.
Flatten it out and then fold it over once. Pat into a 7-8 inch round (about ¾- 1" thick).
With a dough scraper or a sharp floured knife, cut into wedges (6-8).
Gently pull the wedges apart leaving about 1- inch space between the scones.
Bake until fluffy and golden brown, about 12-15 minutes.
Transfer to a cooling rack.
Whisk together the lemon juice and the icing sugar.
Once the scones have cooled off, drizzle mixture over scones.
Freezing the butter makes it easier to grate and combine with the dry ingredients. This in turn creates a flaky texture.
Properly whisk the dry ingredients together. This ensures the uniform distribution of the baking powder.
Resist the urge to over stir the mixture as this will result in the formation of gluten which will in turn create a dense scone.
Adjust the thickness of the lemon glaze to suit your personnel preference.
These are best the day they are made.
Can I use frozen blueberries? Yes. In order to prevent discoloration of the batter, do not thaw them. Please keep in mind that the nutritional information provided below is just a rough estimate and variations can occur depending on the specific ingredients used. *adapted from Better Homes and Gardens