I saw a recipe for heat-resistant buttercream on Craftsy recently, so I decided to try it out and put it to the heat test. To read the original article and see the recipe go here: Stabilizing American Buttercream
Naturally, though, the last few weeks have been fairly cool and not as humid as it usually is this time of year. So I couldn't get the true test of whether the icing would hold up in REAL heat. But I was surprised at how it did behave.
Just looking at the recipe, I was skeptical about how this icing would hold up. The proportions of fat to sugar were strange to me, but it does make sense that not adding any liquid would make the icing less likely to overload on liquid if it started absorbing moisture from the air. What doesn't make sense to me, though, is the fact that it's all butter and no shortening and it's supposed to stand up in the heat better. Hmmmm...
So I used the recipe as it was, and the taste test went really well. My in-house icing testers gave it the thumbs-up and wanted to eat more of it with spoons. The texture was more whippy and light than the butter/shortening version. 4 pounds of sugar filled the mixer the same way that 6 pounds usually do, so there was a lot of puffing up of the icing that happened in the whipping process. It's a really soft icing, too, because of that. It softens faster when taken out of the refrigerator, so again, I questioned the fact that it would hold up in the heat better.
The second step was to ice a cake and see what happened when I stuck it outside. Since it wasn't super hot, though, I can't vouch for the heat-resistance. I can say that it did hold up in moderate heat (about the high 80 degrees Fahrenheit) as well as the butter/shortening version did.
That surprised me, because I thought that the all-butter recipe would just dissolve in any heat at all. If you look at the picture of the two side-by-side, you can see that the one on the left (butter/shortening) actually got shinier than the all-butter one. The surface of the all-butter one on the right stayed pretty matte, while the humidity started getting to the regular formula one.
You can also see the texture of the all-butter one is slightly rough, since it's whipped and has air beaten into it. To get this kind of buttercream really smooth you need to use the hot spatula method to smooth it out, which will melt the surface and get rid of the air fluff texture. I hadn't made any effort to smooth the icing out on either one, but I could tell that the regular formula on the left was looking saggier than the one on the right.
I made a batch with butter that was at room temp, and it was pretty soft, so I added more sugar than the recipe called for. I ended up messing with it until I decided on 6 cups fat to 5 pounds sugar and 4 Tbsp meringue powder. This is a higher fat to sugar ratio than the traditional confectioner's sugar recipe, but it seems to work.
So try this one in a 6 quart mixer, or reduce the amounts for a smaller mixer bowl:
6 cups fat (all butter or your choice of a butter/shortening blend)
5 pounds confectioner's sugar
4 Tbsp meringue powder
Cream the fats, then add 2 pounds of the sugar on low speed. Add another two pounds and turn the mixer on high for about 4 minutes. Reduce the mixer speed and add the final pound of sugar, and mix on high for another minute. You can reduce the speed to low and mix it for a while to try to smooth the texture out a little, but you can also just smooth it out when you ice the cakes.
I can vouch for the fact that this icing holds up well at room temp, but I can't promise that it's heat-stable. The next 98 degree day that we get might not be for a while, but if anyone wants to test it and get back to me I'll post what happens.
Kara Buntin owns A Cake To Remember LLC, online cake supplies at www.acaketoremember.com and www.acaketoremember.etsy.com