Preheat oven to 375°F. Line baking tray with parchment paper.
In a large bowl, whisk together flour, sugar, baking powder, and salt.
Use a box grater to shred cold butter. With a pastry cutter or two forks, mix butter into the flour mixture until crumbly.
In a medium bowl, whisk together egg, milk, and sour cream.
Add egg mixture to flour mixture and combine until just moistened. Add blueberries and mix gently.
Use a cookie scoop or spoon to create 8* equal-sized mounds and place onto lined baking tray. Alternatively, shape dough into an 8-inch circle and cut into 8 equal pieces using a knife or a bench scraper.
Bake for 20-25 minutes, until lightly browned and baked through.
Notes
For 10 scones, bake for 15-20 minutes.
This recipe can easily be doubled to make 16-20 scones.
Keep leftovers in an airtight container at room temperature for 2 days and in the freezer for 3 months.