I came across something that sounded amazing recently--root beer float CAKE! The recipe I planned to use was based on the one from this book. All the comments and reactions to this recipe I'd read on blogs were very encouraging, too, and when I tweeted about the find a few weeks ago, the reaction was just phenomenal.
I baked the cake for my husband's birthday yesterday, using Barq's root beer, which I felt was nice and dark and appropriately bite-y. (I really miss my favorite root beer, which is Old Dominion, but unfortunately it's not a brand we have access to on the west coast.) I made very few changes to the recipe and used our fun little castle Bundt cake pan.
And so, after all that...I'm disappointed to say that the recipe wasn't what I hoped it would be. The cake itself is very moist and has great texture, but the flavor of the root beer is very subtle, almost more like an after taste. I've heard that if you use root beer schnapps (or perhaps extract, as recommended on other sites?) the flavor might be stronger. Overall, the cake was nice and sponge-y, but the flavor wasn't very distinct in either the root beer or the chocolate.
The frosting, though was a complete disaster. The butter and cocoa came together just fine, but once the soda went in the whole thing went a little crazy. I had to add a bit more than the 1/4 cup of root beer recommended just to get it smoother, but even so the texture was just unpleasant and much too sweet. It also melted within minutes, leaving behind a soggy, syrupy mess.
If you're interested in trying out the recipe, I'd recommend trying out root beer schnapps or extract, and perhaps use more chocolate, too, for stronger flavor. As for the frosting, I'd recommend using a very good vanilla buttercream, or perhaps a cream cheese or a dollop of Bailey's flavored whipped cream.
I'm not sure I'd venture to try this again, though...I'm now craving deep, rich chocolate cake to make up for this one. Oh well, sometimes these experiments don't work out to your liking. It's just a bigger deal when it's something as crucial as dessert!