I started with this recipe off the net, modified a bit for ingredients at hand and the addition of yams:
- 1 cup bleached white flour
1 cup whole flour
1 1/4 T baking powder
1 T sugar
some salt (about a teaspoon?)
4 T butter
3/4 cup buttermilk
2/5 of a large yam (could be 2/3 of a small yam)
1. Peel yam, cut into medium blocks about an inch thick. Put in a pot of water and boil, let it simmer...
2. Mix flours, sugar, salt, baking powder in a bowl.
3. Cut 4T butter from stick into smaller portions (about 10) and scatter over the flour mixture. Mix around a little bit, cut up the butter pieces some more.
4. ... get the yam pieces out of the water, let them steam dry for a moment, drop into the bowl. Mix and mash - the hot yam will soften the butter. Mix in the buttermilk.
5. Spread the gooey mixture on a very floured surface, pat out to about 1/2 inch thick, and cut/separate off roundish pieces about 1 index finger in diameter onto buttered/greased cookie sheet.
6. Bake 11 minutes, take out and let cool on cookie sheet for 1-2 minutes.
That's what I did, though when I try this again I may modify it. The amount of yam I put in made the final mixture very gooey and sticky, so I increased the amount of flower and baking powder from the original recipe, but next time I might try with a bit less buttermilk or yam or a bit more flour. Still, despite not looking or feeling like dough, it baked into wonderful biscuits, and the one I took home with me and at just now was still soft and moist.
Edit: As in the original recipe, the oven should be 450 F. Also, I tried a less gooey version with satyrgrl, with whole milk instead of buttermilk, a smaller piece of yam, and slightly more flour. It was pretty good, but the original version was better; I'm not sure if milk vs. buttermilk, or doughy vs. gooey, made the bigger difference.