Combine the dry ingredients together in a large bowl.
Add in the softened butter pats. Gently fold in the sour cream and vanilla.
Carefully mix in the dough together, being extra careful not to overmix it. The dough should be crumbly in texture.
Roll the dough into a rectangular shape. Spread blueberries all over the dough. Fold over the dough, rolling it into a log shape. Cut the scones into similar-sized wedges.
Place scones onto a lined baking sheet, leaving space in between for rising. Brush the tops with whisked egg, followed by a sprinkling of sugar.
Bake at 350°F for 30-40 minutes or until scones are golden brown.