I bought the mix, made by The Cravings Place, from The Gluten-Free Mall - this is a FANTASTIC resource. You order things online and within a few days gluten-free goodness is delivered to your door. This mix had a lot of good reviews so I decided to go for it. It's pretty yummy! The cake itself is a bit dry and gummy (it is gluten-free after all) but the crumble topping covers that right up. I added an extra tablespoon of butter and about 1/3 cup of brown sugar to the crumble topping recipe - there was no way that wasn't going to taste good. It was nice and easy to make and I've already eaten half of it by myself! It's best fresh out of the oven.
:) The Celiac Seal