I’ve iced many cakes over the years and there are quite a few horror stories I can tell you about buttercream icing. Icing sliding off the sides of cakes despite my valiant efforts to fight the forces of gravity. Icing cracking in the fridge on more than one occasion. And once, icing erupting out from between two layers of cake like a newborn alien.
But the point of this Basics post is not to scare you into buying pre-made icings or to make you give up baking your own cakes entirely. Instead, I’m going to give you a formula that will ensure that your icing will never ruin your cakes and your day.
After countless icing disasters, I’ve come to the conclusion that the best buttercream icing is made from 1 part fat (i.e., butter or shortening) and 2 parts icing sugar, by weight, alongside some liquid to thin it to the right consistency. For example, if you use 100g of butter, use 200g of icing sugar and a couple tablespoons of milk.
Volumetrically, that ratio would be 1:4, but I’m a firm believer in the consistency and reliability of measuring by weight instead of cups. (Heck, it was my very first post on Basic Bakes!) Besides, would you rather weigh out butter or squash it into a cup?
There are some things to note about my buttercream ratio. The fat portion can be made up entirely of butter or vegetable shortening, or a combination of both. I’ve already discussed the merits of both in a previous Basics post, but in short, butter is for flavour and shortening is for durability in warmer climates because it doesn’t melt as easily. I tend to use about 60% shortening and 40% butter in my icings to get the best of both worlds. If you want snow-white icing, then use all shortening.
For the icing sugar part, you can substitute part of it for cocoa powder if you’re making chocolate icing. I once read somewhere that you can replace some of the sugar with cornstarch to reduce the sweetness, but I tried it once and my icing was gritty and tasted disgusting.
The liquid part can vary greatly, from water to many forms of liquid dairy like milk and cream. You can even use corn syrup to give your icing a nice sheen. Add enough liquid to your icing to get a nice spreadable consistency. A good sign is when your icing has enough liquid to begin gathering at the bottom of your mixing bowl, but still stiff enough for your beaters to leave trail marks in them.
I can claim that using my buttercream ratio works 99% of the time, but even then, making icing seems to be more voodoo ritual than culinary exploit. If you find your icing is too stiff, just add more liquid. If it’s far too runny, sift in more icing sugar. If it looks like it’s beginning to separate, add in a pat of butter/shortening, whack your mixer on high, and pray to the confectionery gods.