Preheat your oven to 350 degrees, and line a baking sheet with parchment paper. Set aside.
In a small bowl, stir together the blended oats, whole oats, cocoa powder, salt, baking powder, and baking soda. Set aside.
In a medium bowl, beat together the softened butter, sugar, and brown sugar until combined. Add in the egg yolk and vanilla and mix until combined. Slowly add in the dry mixture and beat until combined. Then, fold in the white chocolate.
Scoop the dough into 9 even balls onto the baking sheet. They should be about 1 1/2 tbs each. Press the cookies down just slightly before baking for 10-12 minutes. The cookies will look a little moist in the middle still, but do not over-bake! They will become crunchy as they cool!