16 tablespoons (2 sticks) unsalted butter, frozen whole
1 1/2 cups fresh blueberries or 2/3 cup dried cranberries
1/2 cup whole milk
1/2 cup sour cream
2 cups unbleached all purpose flour
1/2 cup sugar plus 1 tablespoon for sprinkling
2 teaspoons baking powder
1/4 teaspoon baking soda
1/2 teaspoon salt
1 teaspoon grated lemon zest for blueberry scones
Adjust oven rack to middle position and heat convection oven to 400 degrees F. Score and remove half the wrapper from each stick of frozen butter. Grate unwrapped ends of butter sticks on large holes of box grater. (You should grate a total of eight tablespoons.) Place grated butter in freezer until needed. Melt 2 tablespoons of remaining butter and set aside. Save remaining 6 tablespoons butter for another use. Place blueberries in freezer until needed. Whisk together milk and sour cream in a medium bowl; refrigerate until needed. Whisk flour, 1/2 cup sugar, baking powder, baking soda, salt, and lemon zest in a medium bowl. Add frozen grated butter to flour mixture and toss with fingers until thoroughly coated. Add milk mixture to flour mixture, fold with spatula until just combined. With rubber spatula, transfer dough to liberally floured work surface. Dust surface of dough with flour; with floured hands, knead dough 6 to 8 times until it just holds together in a ragged ball, adding flour as needed to prevent sticking. 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 countertop. Lift short ends of dough and fold into thirds again to form approximate 4-inch square. Transfer dough to a plate lightly dusted with flour and chill in freezer for 5 minutes. Transfer dough to a floured work surface and roll into approximate 12-inch square again. Sprinkle frozen blueberries (or dried cranberries if you are making that version) over surface of dough, then press down so that they are slightly embedded in dough. Using bench scraper or thin metal spatula loosen dough from work surface. Roll dough, pressing to form a tight log. Lay seam side down and press log 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. This will make 8 scones. Transfer to a parchment paper lined baking sheet. Or, for smaller scones, you can choose to cut the scones into 16 triangles if desired. Either way you decide to cut them, brush the tops with melted butter and sprinkle with remaining tablespoon of sugar. Bake in a preheated 400 degree F convection oven until tops and bottoms are golden brown, about 15 - 20 minutes. Transfer to a wire rack and let cool 10 minutes before serving. These scones can be made ahead and baked the next morning. Just place the scones on a baking sheet and either refrigerate them overnight or freeze. When ready to bake, for refrigerated scones, bake as directed above. For frozen scones, heat convection oven to 375 degrees F, and extend cooking time to 25 to 30 minutes.