The last time I made a sweet potato pie it didn't turn out all that well, so I was a little nervous about repeating the same mistakes twice. Sweet potatoes are funny. I read somewhere recently that nearly everything we call sweet potatoes are really variations of yams, and true sweet potatoes are in fact, really large and often unseen in our grocery stores. So the last time I made sweet potato pie, I bought what were labeled 'sweet potatoes,' a really pale tuber. Even though I knew the color of a sweet potato pie was supposed to be closer to a pumpkin, I tried to get the right ingredients.