From America's Test Kitchen Season 8: Coffeehouse Treats
Berry scones can be a treat—moist, sweet berries throughout a tender, light biscuit, but more often the berries weigh down the scone and impart little flavor. We wanted a rich, flaky scone studded with sweet, juicy blueberries.
Starting with traditional scone recipes, we increased the amounts of sugar and butter to add sweetness and richness to our scones. A combination of sour cream and milk lent both richness and tang. But now our scones were heavier than we wanted. We found two ways to lighten them. First, we borrowed a technique from puff pastry, where the dough is turned, rolled, and folded multiple times to create layers that are forced apart by steam when baked, and added a few quick folds to our scone dough. Then, to ensure that the butter would stay as cold and solid as possible while baking, we froze the butter and grated it into the dry ingredients on a box grater. Both tricks made for lighter, flakier scones. Adding the blueberries was a challenge. If we put them into the dry ingredients, they got mashed when we mixed the dough; when we added them to the already-mixed dough, we ruined our pockets of butter when we worked the berries in. The solution was pressing the berries into the dough, rolling the dough into a log, then pressing the log into a rectangle and cutting the scones. We had successfully transformed the scone into a fruit-filled, rich yet light treat.
It is important to work the dough as little as possible—work quickly and knead and fold the dough only the number of times called for. The butter should be frozen solid before grating. In hot or humid environments, chill the flour mixture and workbowls before use. While the recipe calls for 2 whole sticks of butter, only 10 tablespoons are actually used (see step 1). If fresh berries are unavailable, an equal amount of frozen berries (do not defrost) can be substituted. An equal amount of raspberries, blackberries, or strawberries can be used in place of the blueberries. Cut larger berries into 1/4- to 1/2-inch pieces before incorporating. Refrigerate or freeze leftover scones, wrapped in foil, in an airtight container. To serve, remove foil and place scones on a baking sheet in a 375-degree oven. Heat until warmed through and recrisped, 8 to 10 minutes if refrigerated, 16 to 20 minutes if frozen. See final step for information on making the scone dough in advance.