When you’re making any type of meringue buttercream, you need to equalize the temperatures between the hot sugar syrup and the cold butter.
If you have too much of a difference between them, the heat can melt the butter, or the cold butter can break into small pieces and create what looks like cottage cheese.
That will keep the icing from emulsifying, which is where the water and the oil in it are balanced and form a smooth mix.
If you do miscalculate and end up with a broken buttercream, you can save the icing by evening out the temperature, but it won’t be the same consistency that it would have been if it worked the first time.
(For an article about what happens if you get egg yolk in your meringue, click here!)
The trick to fixing a broken buttercream is to warm it up if it’s too cold, or to cool it off if it’s too soft and soupy.
The easiest way to do this is to wrap the mixer bowl with either a warm cloth or with cold ones, or ice packs, to either heat up or cool off the mixer bowl while you whip the buttercream.
How to fix a curdled-looking buttercream.
For a broken buttercream that looks curdled, you’ll want to wrap the bowl with warm cloths and keep changing them if they cool off.
Patience is key here, because it takes time to warm up the butter enough to basically melt it slowly as the whip is moving in the bowl and combining the icing together.
Run hot water over a dishcloth and wrap it around the bowl, and turn the mixer on high with the whip attachment.
Keep adding hot water to the cloths as they cool off and eventually the buttercream will smooth out and you’ll be able to use it.
How to fix a melted buttercream
The opposite principle can be used if the buttercream is soupy, which means that it was too hot.
Just cool it off for a bit in the fridge then whip it, or pack cold cloths or ice packs around the mixer bowl while you whip it.
This usually takes longer than a curdled buttercream to fix because the heat from the beater will work against the cooling of the cold water or ice.
Sometimes it’s fastest to put the mixer bowl in the fridge, then rewhip it when it cools down a little.
You don’t want it to get totally solid, though, then you’ll end up with the same problem of it being too cold to whip. You jsut want to cool it down to room temperature.
Any buttercream that you have to fix this way is going to be a little thicker than icing that worked the first time, so you could have trouble smoothing it out on a cake.
I used to use broken buttercream as fillings because those don’t need to be as smoothable on the outside of the cake.
Here’s a video that I did of how to fix a broken or soupy buttercream:
This was an Italian meringue, but the principles are the same for any kind of meringue buttercream that can separate if the butter is too cold.