Preheat your oven to 400°F / 200°C. Lightly butter a large baking sheet or line it with parchment paper.
In a large bowl, combine the rolled oats and buttermilk (or yogurt).
Let the mixture soak for 15 minutes to soften the oats. 2.
While the oats are soaking, whisk together the whole wheat flour, all-purpose flour, brown sugar, baking powder, baking soda, and salt in a separate medium bowl. 3.
Using a pastry blender or your fingertips, cut the chilled butter into the flour mixture until it resembles coarse crumbs with some pea-sized butter pieces remaining. This is key for a flaky texture. 4.
Add the lightly beaten egg to the soaked oatmeal mixture and stir to combine.
Pour the wet into the dry and mix with a fork just until a shaggy dough forms.
Do not overmix. 5.
Turn the dough out onto a lightly floured surface and gently knead 4-5 times, just enough to bring it together into a cohesive ball.
Pat the dough into a circle about ¾-inch thick. 6.
Using a sharp knife dipped in flour, cut the circle into 8 equal wedges.
Arrange the scones a few inches apart on your prepared baking sheet. 7. For a glossy, golden-brown finish, whisk together the remaining egg and 1 teaspoon (5 ml / 0.2 fl oz) of water.
Brush this egg wash over the tops of the scones. 8.
Bake for 15 to 17 minutes, or until the scones are risen and golden brown.
Serve immediately while warm, or let cool on a wire rack.
Keep your , especially the butter and buttermilk, as cold as possible. This creates steam pockets while baking, resulting in light, flaky layers.