How to Make It
Preheat oven to 375°.
Spread oats on a baking sheet; bake at 375° for 10 minutes. Cool 5 minutes.
Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine oats, flour, and next 4 ingredients (through salt) in a medium bowl; cut cold butter into flour mixture with a pastry blender or 2 knives until mixture resembles coarse meal. Add chocolate chips, cherries, and blueberries, tossing to combine. Add buttermilk, stirring just until moist (dough will be sticky).
Turn dough out onto a lightly floured surface; knead lightly 4 to 5 times with floured hands. Pat dough into a 7-inch circle on a baking sheet lined with parchment paper. Cut dough into 8 wedges, cutting into but not through the dough.
Combine egg white and 1 teaspoon water in a small bowl, stirring with a whisk. Lightly brush egg white mixture over surface of dough; sprinkle evenly with turbinado sugar. Bake at 375° for 25 to 28 minutes or until golden.