In my cooking experience, I've mangled many a recipe. Often it's from not having the right ingredient and trying to substitute; sometimes it's because Stephen has snuck up behind me and added an extra pinch of salt or sprinkling of raisins because he doesn't think I'm doing it right. And sometimes, I have no idea why it hasn't worked out.
Take this birthday cake for example. The chocolate cake recipe is a favourite of mine, and has become a staple - no problems there, it turned out dense and moist the way I like it. The chocolate ganache, however, was being bitchy and we couldn't work out why it wasn't thickening. After many attempts at cooling it down, we finally decided to try whipping it - I mean, it IS half cream, why the hell not?
As you can see, the results were favourable:
If you don't know how to make ganache, here's a handy little recipe. Then, when it's cool to the touch but not thickened to the point of usual ganache, whip with a hand-held mixer for 30 seconds to a minute. Spread promptly onto cake of choice!