I think it's sometimes available at Starring Rolls. They used to give out the recipe printed on a card the shape of a Derby. Very cute. I had the recipe but never tried it.
We were quite disappointed the last time we had it (and we used to love it). It seems it is now baked off-site by a third party contractor and then frozen. Unfortunately, it tastes like it. As far as I know, they no longer give out the recipe because apparently it's not made on site any longer, and I doubt the current recipe bears any relation to the original one.