I made the caramel cake in this month's food and wine magazine:
the cake came out beautifully, but the icing didn't work, it was too runny. i mixed it until cool but it wouldn't thicken. a friend of mine had made a similar cake the week before - hers didn't work either, but she had the opposite issue - the icing was hard and crystallized and crumbled like praline.
we compared recipes and the major difference was that my recipe said to cook the caramel to 235 - which is just below soft ball stage. her recipe said to cook the sugar to 248. so i put the icing back into the pot even though i had added the butter already and cooked it until it was 248. when i placed it in the mixer it immediately began to thicken and take on a crystallized appearance, although it did not harden or crumble. it stiffened as soon as i began spreading it but i was able to get it onto the whole cake. it ended up being incredible - perfect smooth but slightly sugary (in the that powdered sugar buttercream way) consistency and amazing flavor.
i tried to make it again this week, and the icing didn't work. i followed the recipe but cooked the icing to 248, and then added the butter and cream. it was gooey and soft and chewy like melted caramel candy. it was much darker than the 1st batch. i even tried putting it back on the heat. but it never set up.
now...i don't actually know what the texture is supposed to be like, having never had this cake before. and...i am a professional pastry chef and i can't for the life of me figure this out and i am becoming very frustrated not knowing how to achieve the same results.
any suggestions? recipes i have found in other threads use descriptive terms like "boil down low" and "cook for 20 minutes" and such.