Blueberry Scones

1. Adjust oven rack to middle position and heat oven to 425 degrees. Line baking sheet with parchment paper. Remove half of wrapper from each stick of frozen butter. Grate unwrapped ends (half of each stick) on large holes of box grater (you should grate total of 8 tablespoons). Place grated butter in freezer until needed. Melt 2 tablespoons of remaining ungrated butter and set aside. Save remaining 6 tablespoons butter for another use. Place blueberries in freezer until needed.
2. Whisk milk and sour cream together in medium bowl; refrigerate until needed. Whisk flour, 1⁄2 cup sugar, baking powder, baking soda, salt, and lemon zest in medium bowl. Add frozen grated butter to flour mixture and toss with fingers until butter is thoroughly coated.
3. Add milk mixture to flour mixture and fold with rubber spatula until just combined. Using spatula, transfer dough to liberally floured counter. Dust surface of dough with flour and with floured hands, knead dough 6 to 8 times, until it just holds together in ragged ball, adding flour as needed to prevent sticking.
4. Roll dough into approximate 12-inch square. Fold dough into thirds like a business letter, using bench scraper or metal spatula to release dough if it sticks to counter. Lift short ends of dough and fold into thirds again to form approximate 4-inch square. Transfer dough to plate lightly dusted with flour and chill in freezer 5 minutes.
5. Transfer dough to floured counter and roll into approximate 12-inch square again. Sprinkle blueberries evenly over surface of dough, then press down so they are slightly embedded in dough. Using bench scraper or thin metal spatula, loosen dough from counter. Roll dough into cylinder, pressing to form tight log. Arrange log seam side down and press into 12 by 4-inch rectangle. Using sharp, floured knife, cut rectangle crosswise into 4 equal rectangles. Cut each rectangle diagonally to form 2 triangles and transfer to prepared baking sheet.
6. Brush tops with melted butter and sprinkle with remaining 1 tablespoon sugar. Bake until tops and bottoms are golden brown, 18 to 25 minutes. Transfer to wire rack and let cool for at least 10 minutes before serving.
   TO MAKE AHEAD: After placing scones on baking sheet in step 5, either refrigerate them overnight or freeze for up to 1 month. When ready to bake, for refrigerated scones, heat oven to 425 degrees and follow directions in step 6. For frozen scones, do not thaw, heat oven to 375 degrees and follow directions in step 6, extending cooking time to 25 to 30 minutes.

FOLDING AND SHAPING BLUEBERRY SCONES
1. Fold dough into thirds (like business letter).
2. Fold in ends of dough to form 4-inch square, then chill dough in freezer for 5 minutes.
3. Reroll dough into 12-inch square, then press berries into dough.
4. Roll dough into jellyroll-like log to incorporate blueberries.
5. Arrange log seam side down and press into even 12 by 4-inch rectangle.
6. Cut dough crosswise into 4 rectangles, then diagonally to make 8 triangular pieces.