Cook's Illustrated Blueberry Scones

Directions

1. Adjust oven rack to middle position and heat oven to 425 ℉. Stash the blueberries in the freezer to firm slightly while preparing the scones. Grate 8 T. of the frozen butter on the large holes of a box grater, working quickly as to not soften it. Keep in the freezer until ready to use. Melt the remaining 2 T. of butter and set aside. Whisk together the milk and sour cream in a separate bowl and refrigerate until needed. Whisk the flour, ½ c./3 ½ oz. of the sugar, baking powder, baking soda, salt and zest in a medium bowl. Add the frozen butter and quickly toss with fingers until thoroughly coated. The butter and flour should be incorporated, but the butter should still be whole and frozen. It's a fussy procedure, but it is essential to the final "flake factor", if you will.
2. Add the chilled milk mixture to the dry ingredients and fold with clean hands until just combined. Transfer the dough to a liberally floured work surface. Lightly dust the dough with flour and with floured hands, knead 6 - 8 times until it just holds together in a ragged ball, adding flour as needed to prevent sticking. With a floured rolling pin (or a handy wine bottle), roll the dough into an approximate 12" square. Fold the dough, like a business layer, into thirds using a bench scraper to assist in releasing the dough from the work surface. Then, form an approximate 4" square by folding the ends into the middle, into thirds again. Transfer dough to a lightly floured plate (or a paper plate, like I use) and chill in the freezer for 5 minutes.
3. Transfer the dough back to your work surface, continuing to flour as needed, and roll into an approximate 12" square again. The dimensions aren't really important, but you will need enough surface area for the next step: Sprinkle the blueberries evenly over the surface of dough, then press down lightly to just merely embed them into the dough. Using a bench scraper, lift one end of the dough, beginning to roll into a tight log. Lay, seam-side down, and press the log into a 12" by 4" rectangle. Using a sharp, floured knife (or even the bench scraper you've been using), cut the rectangle lengthwise into 4 equal portions. Cut each square in half diagonally to end up with 8 triangles, transferring each to a parchment-lined sheet pan.
4. *Note: After shaping and cutting, the scones can be frozen and transferred to a ziplock freezer bag for long term storage. Bake from frozen, adding 3 - 5 minutes onto the total baking time.
5. Brush each triangle top with the reserved melted butter and sprinkle evenly with the remaining tablespoon of sugar. Bake until tops and bottoms are golden brown, 18 - 25 minutes, rotating the pan halfway through. Transfer to a wire rack and allow to cool for at least 10 minutes before serving.