Preheat the oven to 180°C (356°F).
Finely chop yuja (yuzu) and yam (sweet potato).
In a bowl, mix bread flour, baking powder, salt, and stevia.
Add cold butter and rub it in with your hands until the mixture resembles coarse crumbs.
Add the chopped yuja and yam, then pour in the milk to form a dough.
Gather the dough and roll it out to 2cm thick; cut into triangles.
Line a baking tray with parchment paper and place the scones on it.
Bake in the oven at 180°C (356°F) for 18-20 minutes until golden brown.