Kitchen Mysteries is a weekly exploration of oddities surrounding cooking and food. They could be recipes that fail when they shouldn't, conflicting advice from different sources, or just plain weirdness. If it happens in a kitchen, and you're not sure why, send a tweet to The Food Geek to find out what's happening.
From Twitter, Kristin asks:
I am not surprised that you have trouble with the Swiss and Italian buttercreams, for they are the most ambitious of the buttercream frostings. Finecooking.com has a Classic Buttercream recipe that is essentially an Italian Buttercream. As this is a classic recipe, it doesn't take advantage of many of the modern advances that will make life easier for your buttercream making ways. Before we can discuss those, we must find out what the problem is.
A buttercream frosting is a classic way of covering a cake. Buttercreams are generally butter, sugar, some manner of egg product, and maybe a non-butter dairy product, with some specialized ways of combining them. Sweet, buttery, and generally well worth putting on a cake. In the case of the Swiss and Italian buttercreams, the egg product is an egg-white foam, which is folded into the butter. In the case of the Italian buttercream specifically, a hot sugar syrup is poured into frosting.
When you make a buttercream, you're making an emulsion, which is a combination of two liquids that generally don't mix. It's the classic case of "oil and water." In this case, the oil is coming from the butter. Oil is very cliquish, as is water, and it's frowned upon for individual water molecules to be seen with oil groups and vice versa. In the case of a buttercream, you're attempting to get water to sit at oil's table at lunch, and it's just not happening.
What's needed here is The Popular Kid. The Popular Kid can cross boundaries of class and clique, and can rearrange the whole lunch scene with a minimal fuss, because everyone likes The Popular Kid. The Popular Kid is an emulsifier.
You may have heard that eggs contain emulsifiers, and thus the buttercream should be easy to make. Were you making a French buttercream, this would be correct. The French use egg yolks for their buttercream, and thus they get all of the lecithin in the egg yolk to invite water over to oil's table so that they can talk about prom or something. In a strange twist of events, the Italians and the Swiss have actually made their buttercreams more difficult to create than the French, which makes me wonder if these names are indicative of their origin or just labels thrown on later.*
We need an emulsifier, and we don't want to go to the gourmet store to find some soy lecithin or anything like that. In the case of tricky recipes like this, I will generally turn to Shirley Corriher first for inspiration, and she succeeds admirably in her new book Bakewise. She suggests substituting a cup of the butter with 2/3 cup of shortening such as Crisco. She says many of the baking shortenings contain emulsifiers already, which makes life so much easier in these situations. You may also want to stabilize the egg foam by putting in a teaspoon of cream of tartar.
Other ways a buttercream can fail is if you don't let the butter get warm enough. You need it room temperature so that the water can actually incorporate into the butter. If you are making an Italian buttercream where you are making your own syrup from sugar and water, you want to ensure that the syrup gets to 248°F, a.k.a. the hardball stage. As those who read though my analysis of the problems associated with toffee may recall, the temperature that you heat the sugar to controls how much water is in the mixture. So if you don't heat the syrup enough, you will have too much water, and it won't necessarily all incorporate properly.
There are more possibilities, but this covers the highlights. I highly recommend starting with the Swiss buttercream, as that should be the easier of the two. Make sure that the butter is soft but not melted, put a little cream of tartar in the egg whites, and swap out some butter for a bit of shortening with an emulsifier such as TBHQ in it.
Give all that a try, and please let me know if it works or not. If not, we can try to analyze more in-depth what happened. If it does work, then let me know what you tried.
*- In the case of the Swiss and Italian buttercreams, I believe the names come from the type of meringue that is incorporated into the butter. Italian meringue has the syrup, while a Swiss meringue does not.