Buttery, flaky scones studded with berries make breakfast special.
Adjust oven rack to upper-middle position and heat oven to 425 degrees. Line rimmed baking sheet with parchment paper.
In medium bowl, combine berries and confectioners’ sugar. Use rubber spatula to stir to coat berries with confectioners’ sugar. Place bowl in freezer until needed.
Place flour, chilled butter, sugar, baking powder, and salt in food processor. Lock lid in place. Hold down pulse button for 1 second, then release. Repeat until butter forms pea-size pieces, six to eight 1-second pulses.
Remove lid and carefully remove processor blade (ask an adult for help). Transfer flour mixture to large bowl. Use rubber spatula to stir in frozen berries until they are well coated.
In second medium bowl, whisk milk and egg yolk until well combined. Add milk mixture to flour mixture and use rubber spatula to stir until just combined into shaggy dough. Do not overmix.
Sprinkle clean counter lightly with extra flour and coat your hands with flour. Transfer dough to floured counter and shape dough into 8 scones. Use bench scraper (or spatula) to transfer scones to parchment-lined baking sheet.
Use oven mitts to remove baking sheet from oven (ask an adult for help). Place baking sheet on cooling rack and let scones cool on baking sheet for 15 minutes.
One key to flaky, tender scones is the ingredients you use, but another is the temperature of those ingredients. Using chilled butter—and mixing everything together quickly, before it warms up—helps create those perfect flaky layers. Using frozen berries helps keep the dough’s temperature low. It also prevents the bright berry color from bleeding out of the berries and into the dough. If you don’t like mixed berries, you can use 1 cup (5 ounces) of frozen raspberries, blueberries, or blackberries instead of the mixed berries.