Why are my dumplings made of evil? I made a fairly simple chicken-and-dumpling stew recipe; however, after one bite of dumpling, I have the most wretched aftertaste. The soup is fine; however, the dumplings taste totally nasty, kind of bitter and repulsive and a little like vomit (My fiancee describes it as "metal and bad"). If there had been anything in my mouth by the time that taste hit, I'd have spit it out instinctively. 

The recipe calls for 1/3 cup Bisquick Heart Smart baking mix and 1/3 cup buttermilk to make the dumpling dough; I doubled it because I was making a large pot of stew. The stew tastes fine once I ditch the dumplings; it contained chicken broth (made from bouillon cubes), milk, cornstarch, cooked chicken, parsnips, carrots, celery, and onions. The dumplings were dropped by spoonfuls into the stew and cooked for about 7 minutes, as per the recipe directions. I have not made this specific recipe before. The consistency of the dumplings seemed fine; they were a little bland due to lack of seasoning, but otherwise all was well until that aftertaste hit. 

What could have gone wrong? The buttermilk was purchased just a few days before, well within its expiration date (Nov 24th), and the baking mix had been used for pancakes earlier in the week (which were a little bland but not disastrous)
Spoiled buttermilk wouldn't give a metallic aftertaste, but I wouldn't expect old baking mix to do so either. 

I would suspect that your box of bisquick is either contaminated, or you may have gotten a bad box. Sometimes manufacturing processes don't go right, so it might be that your box got far too big a portion of baking powder, or some other component of the mix. In the manufacturing process all the ingredients are supposed to be well mixed but it isn't unheard of for a clod to make it through the process intact. I'd throw the box out.