In the mixing bowl, stir to combine the all-purpose flour, whole wheat flour, oats, baking powder, sugar, and salt. Add the cold butter and mix at the lowest speed and mix until the butter is in pea-sized pieces.
Lightly beat 4 of the eggs. Stir together the buttermilk, maple syrup, and 4 eggs. Pour into the the flour-and-butter mixture and stir with a heavy wooden spoon just until blended. The dough may be sticky, but if it's too sticky you can dust on a little additional flour.
Dust the work surface with plenty of flour and dump ⅓ of the dough. Flour your hands and gently work the dough to make sure the ingredients are thoroughly combined. Pat the dough into a circle ¾- to 1-inch thick. You should see lumps of butter in the dough. Cut the dough into 6 triangles and place them on the baking sheet.
Whisk together the last egg and the milk to make an egg wash. Brush the scone tops with egg wash. Bake for 20 to 25 minutes, until the tops are crisp and the insides are done. Remove from the pan and cool on a wire rack. Toast about 2 tablespoons of quick oats for a topping.
GLAZE: Stir together the confectioners' sugar, maple syrup, and vanilla. When the scones are done, cool for 5 minutes, and drizzle 1 tablespoon of glaze over each scone and quickly garnish with a few sprinkles of the toasted quick oats. The glaze sets quickly, so sprinkle on the oats immediately if you want it to stick to the glaze.
VariationsAdd ¾ cup of raisins (75 g) or small-diced pecans (85 g).Plain yogurt works as a substitute for the buttermilk.Cut the scones into rounds instead of triangles.