Place potato into simmering basket and pour water over. Cook 20 min/100ºC/speed 3. Remove simmering basket and cool potato.
Preheat oven to 200ºC and line a flat baking tray with paper.
Place wheat into clean and dry Thermomix bowl and mill 1 min/speed 10. Set aside.
Place butter and sugar into Thermomix bowl and blend 5 sec/speed 5.
Add remaining ingredients except including cooled potato and mix for 6 sec/speed 6.
Knead 30 sec/dough setting/Interval.
Roll out dough on well floured Silpat mat and cut into rounds using floured scone cutter. Brush scones with milk, and bake for 15 minutes until golden. This is quite a sticky dough, but try to manage it without adding extra flour as this means a beautiful fluffy scone as the end result. (And don't we all want fluffy in our scone??)
Serve hot with the obligatory butter, lemon curd, jam, whipped cream or mascarpone.