The baked sweet potato had already been pushed through the fine screen of a ricer, so was ready to go. I used White Lily all-purpose flour, not wanting to go buy the self-rising, and added the necessary salt and baking powder (had to borrow a little from my sister-in-law, who had (gasp) the kind with aluminum in it...though I suspect I'll never taste it). I grated the butter in frozen, then crumbled and squished the bits by hand to get a more uniform mixture. Next time, I think a food processor would do this better, as the goal does not seem to be to retain any butter flakes like many biscuit recipes do.
Next to go in are yolks from hardboiled eggs, and I bought the prepackaged "small" eggs from the deli department and found that 3 of these gave just a bit over the specified 37 grams that 2 large eggs are supposed to produce. The yolks are pressed through a strainer into the flour-butter mixture, and whisked to blend.
The wet ingredients of sweet potato and either heavy cream or buttermilk (I had whole-milk buttermilk) are beaten together, then added to the dry and stirred around to get a sticky dough. The dough is covered and let rise until puffy, about 1-1/2 hours. That's a difference from my whole-wheat angel biscuit recipe, which don't get any rising time for the yeast to work, and I may have to try this technique on the whole-wheat version--or alternatively, try baking the sweet potato biscuits with no rising time. Once puffy, the dough is patted down in its container and moved to the refrigerator for at least 4 hours, or up to 3 days. I made the dough on Sunday night before a work trip on Monday, so mine got to wait 4 days, until Thursday night. But I forgot about them, so it was actually Friday afternoon, and the dough had a nice tangy smell.
As I've been doing with several quick breads recently, I rolled the dough out to the right thickness (after a quick kneading), then just cut it into squares being careful to use a straight cut and not seal the edges. I like this because it avoid any re-rolling and scraps...but it didn't work well here as the biscuit edges that weren't cut kept those sides from rising well. Next time I'll use a biscuit cutter, or maybe trim the edges before cutting out my squares if I think I can have fewer scraps that way.
The biscuits rise after being cut out, then finally get that baking. The results are very nice and fluffy rolls with a strong orange color, but I didn't get much if any flavor from the sweet potato. These would make a nice dinner roll when you want to add color to the table, perhaps for Thanksgiving when sweet potatoes are a traditional part of the meal.