The absolute best part of this job is research. Frosting research. Caramel Frosting research!
I have tried several versions of Caramel Frosting and the winner is Martha Stewart's Dark Brown Sugar Swiss Meringue.
What I was searching for was a creamy caramel flavor, without a super sugary taste. So that rules out every recipe that adds powdered sugar. Those were too sweet and somehow never fully incorporated the sugar, so a little crunchy.
Then there are the cooked caramel frostings. You know, the kind you think of when someone says Caramel Cake. Cake Doctor has a Quick Caramel Frosting that is nice, but this frosting tend to harden quickly. And they are not silky. And if you mess up, the frosting gets crunchy. Alton Brown did a whole episode on the science of Caramel.
Allrecipes.com has this Caramel Frosting V that I really do love. The only downside is that you have to start a day in advance. Let the butter/cream mixture cool completely in the fridge overnight. And then, if it is too humid, the frosting might not whip up without 4 cups of powdered sugar. I think I've mentioned how I feel about that!
My second favorite and go-too in a pinch is Caramel Marshmallow Meringue. I found the recipe here, Abby calls it Shortcut Marshmallow Buttercream. Add a tablespoon or two of caramel sauce and instant delicious creamy frosting. Ok, so there is 3/4c powdered sugar. But it does melt into the fluff. Worth noting about this recipe: you can not double it. Somehow when you try to double this recipe, it gets too soft, not pipe-able. And it takes about 2 batches to frost an 8" cake.
That brings us to Martha Stewart's Dark Brown Sugar Swiss Meringue. It is everything I was looking for in a Caramel Frosting. Not too sweet, creamy, deep caramel flavor and one batch is plenty to cover an 8" inch cake. Takes about 30 mins to make. One hint to make this recipe fool proof: when you start to whip the egg white/sugar mixture wrap the outside of your bowl in ice packs or frozen veggies. I used canned vegetables to hold the ice bags in place. It cools the frosting to the right temp to add the butter.
To add to the caramel-i-ness, I gently poured caramel sauce over the chilled cake just enough to run down the sides.