Before making the scones, you'll need to cook the sweet potato. I prefer roasting them, but you can also boil them or use cooked canned sweet potato. This step can be done the day before, as the mashed sweet potato needs to be cold for the scone dough.
To roast the sweet potato, preheat the oven to 425F. Wash and scrub your sweet potato, then pat and dry with a towel.
Add the sweet potato to a tray and use a fork to pierce small holes in the sweet potato. This allows steam to escape while roasting and prevents it from exploding.
Roast for 40-60 minutes or until cooked through. They are ready when a knife can easily be inserted without any resistance and they are soft inside.
Let the sweet potatoes cool for about 10 minutes. Then peel off and discard the outer skin.
Add the sweet potato flesh to a bowl and mash with a fork until smooth. The mashed sweet potato must be cold before using in the scone dough, so add the bowl to the fridge to cool completely.