2 cups all-purpose flour
1/3 cup sugar
1 t baking powder
1/4 t baking soda
1/2 t salt
8 T unsalted butter, frozen
1/2 cup blueberries
1/2 cup sour cream
1 large egg
1. Adjust oven rack to lower-middle position and preheat to 400 degrees.
2. In a medium bowl, mix flour, 1/3 cup sugar, baking powder, baking soda and salt. Use food processor to work in butter to flour mixture (mixture should resemble coarse meal).
3. In a small bowl, whisk sour cream and egg until smooth.
4. Using a fork, stir sour cream mixture into flour mixture until large dough clumps form. Add blueberries. Use your hands to press dough against the bowl into a ball.
5. Place on floured surface and pat into a 7 to 8-inch circle about 3/4-inch thick. Sprinkle with 1 tsp of sugar. Cut into 8 triangles; place on a cookie sheet lined with parchment paper about 1 inch apart. Bake until golden, about 15 to 17 minutes. Cool for 5 minutes and serve warm or at room temperature.