Some cakes are tasty enough to stand on their own, but almost all of them benefit from a bit of icing on top. A tub of the store-bought kind will work, but real homemade buttercream is much richer and tastier. Even fancy European-style icings are within the reach of a home baker who's good at following a recipe, but both simple and complex icings will occasionally separate or "break." Don't throw it out when this happens because there's usually an easy fix.
Types of Buttercream
A lot of different frostings are referred to as "buttercream," but they're made differently, and that means they curdle for different reasons. You need to know which is which before you dive into the sea of fix-it tips on the internet. The most common buttercream frostings break down into three types:
- Basic/Decorator's/American Buttercream: This is the one you probably grew up with. It's very simple, with just butter –some recipes use shortening as well or instead – plus confectioner's sugar, flavorings or colors, and a splash of milk to loosen it.
- Meringue Buttercreams: These are lighter and fluffier, and they're made by mixing hot sugar syrup with egg whites, and then beating softened butter into the resulting meringue. The end result is a soft, fluffy icing that's surprisingly durable. Italian and Swiss buttercreams fall into this style.
- French Buttercream: The richest of them all, this one's made with egg yolks instead of whites. You drizzle hot sugar syrup into the yolks and beat them until they're light and foamy, then incorporate the butter.
These differences in methods and ingredients mean that the icings break for different reasons, so you'll need to use different fixes for each.
Fixing American Buttercream
If you're making this simplest of icings, curdled buttercream usually happens only for a couple of reasons. One is simply that you haven't beaten it enough, yet. You'll often need to mix the ingredients for 10 minutes or longer before they come together properly. Inexperienced bakers often give up too soon. This is especially true if your butter was too cold when you started mixing. The friction from the mixing process will eventually warm the butter to the point that it incorporates properly.
Another possible issue is that you've added too much liquid in the form of milk or flavorings. Buttercream is an emulsion of fats and liquids, and you may have added more liquid than the icing can handle. To fix it, just add a tablespoon or two of shortening and keep beating. It should come back together.
A third issue afflicts only recipes that combine shortening for stability and butter for flavor. Sometimes the two fats don't mix properly, often because the instructions tell you to have them at the same temperature. Shortening is stiffer than butter at room temperature, though, so it's more accurate to say they should be at the same texture. If you poke each ingredient with your fingertip, they should feel the same. To fix this, warm the bowl gently as you beat it, just until the ingredients come together.
Fixing Egg-Based Buttercreams
Egg-based buttercreams, whether made with the whites or the yolks, are very temperature sensitive, so when they break, temperature is almost always the problem. It's really important to wait until the egg and sugar mixture is cool to the touch before you add the butter, otherwise it will break.
To repair the broken egg-based buttercream, you'll need to either make it warmer or cooler. Its appearance will tell you which. If it's lumpy, with bits of visible butter in it, it's too cold. Keep beating, and if that doesn't work, you can gently heat the mixer bowl by blowing on it with a hair dryer or – if you're using a hand mixer – setting the bowl over another bowl or a pot of warm water until the icing comes together.
If your icing is loose and soupy, it's too warm or you didn't cool the eggs enough before adding the butter. This is also an easy fix. If you're using a stand mixer, refrigerate the bowl for 10 to 20 minutes until there's a stiff layer of icing stuck to the inside of the bowl. When you start mixing again, that'll combine with the too-soft icing in the middle of the bowl and they'll arrive at the right temperature. If you're working with a hand mixer, you can set your mixing bowl in a bed of ice water and keep whipping until it comes back together.