DD's 9th birthday cake. Involved more green food colouring than you can possibly imagine.
My most recent disaster involved cookies. We had a bake-off at work, and I'd invented Sticky Toffee Pudding cookies, bases on my friend's basic cookie recipe. I'd made one batch, involving various dark sugars, dates, pecans, and fine-tuned it for the big day. The texture was a little odd, but they tasted good, so they went in for judging.
Meanwhile, in a chatroom, my friend is asking for the recipe so she can add it to her blog (she wanted to post recipes based on her book). I reeled off the recipe, and she responded with the fatal words:
"Baking powder?"
ARGH.
Cos yes, the reason I'd forgotten baking powder in the recipe was that I'd forgotten it in the cookies. Which accounted for the funny texture.
All th bake-off goods were sold for charity; I bought back half my batch of weird cookies and made my colleagues eat them. 