Anytime I refer to buttercream on this blog, I usually start here. I thought I'd posted this recipe, but I can't find it, so I'll publish in a separate, bookmark-it-please post.
Buttercream is a very broad term used to describe all sorts of fillings/icings make with butter. Heck, sometimes people even call them buttercreams if they are made with Crisco. But, I don't do Crisco. Simple buttercreams (the kind you might find on a cake from a grocery store) are usually a mixture of butter/Crisco plus powdered sugar. They tend to be somewhat grainy, very sweet and hold up well to decorations. If they are part or all Crisco, they also stand up well to heat. (Butter melts, Crisco doesn't.)
More complex buttercreams involve cooking eggs (whites or yolks or both) with sugar to create a meringue, which is a very stable base for a buttercream icing. A meringue is basically a mixture of egg whites and sugar. For buttercreams, the meringue base (either Swiss or Italian style) is heated for safety and stability and later mixed with butter. The meringue produces an icing with a smoother, lighter texture, a less-sweet taste and a beautiful shine. There are two major differences between Italian Meringue and Swiss Meringue. In a Swiss Meringue, the egg whites and sugar are mixed together and the mixture is heated, usually over a double-boiler (indirect heat) to a temperature of 140 F (just almost too hot to touch and, significantly the temperature needed to kill salmonella). The mixture is then whipped until cool. This is a Swiss Meringue. To make an Italian Meringue, the egg whites are whipped separately while the sugar is heated with a little water to make a hot sugar syrup. This syrup is cooked to around 243 F (just at the end of the soft-ball stage) and then poured over whipping egg whites to form a very stable, glossy meringue. Once the meringue is cool, the butter can be added, along with any flavorings or additions. This is where it always starts!
Italian Meringue Buttercream
My basic formula is:
x oz egg whites
2x oz sugar + enough water to moisten
2-3x oz butter
A really awesome thing about this recipe is that it can be made with any quantity of egg whites you have on hand and scaled up or down based on how much buttercream you need. So, for example, one large egg white weighs/measures about an ounce. When I separate 4 eggs, I have about 4 ounces of egg whites (save your yolks in another container with plastic wrap on the surface). Place the egg whites in a mixer bowl (may want to add a pinch of cream of tartar to help with stability and volume). In a saucepan, use double the weight of sugar, so in this example 8 oz sugar (if you don't have a kitchen scale, you can look up the weight of 1 cup of sugar and, guess what?!? One cup of sugar weighs 8 oz.) I do use a kitchen scale religiously, which makes things easier if, say, your 4 egg whites come out to 4.4 oz and you need to use 8.8 oz sugar. A scale makes things a little more exact.
Using the instructions above, mix in just enough water to the sugar to moisten the sugar, begin to cook over high-medium heat. (At this time, also begin whipping your egg whites on medium speed.) You can use a candy thermometer or, if you don't have one, you can use visual cues or the ice water test for the sugar stage. Once the syrup reaches close to the soft-ball stage, you will notice that the bubbles on the surface of the syrup begin to get larger and slow down. Once at that stage you can grab a very small amount out of the hot syrup (you can use a fork or your fingers, but in that case be careful not to go in for more than a second) and drop it into a nearby cup of very cold/ice water. The drop of sugar syrup should form a soft ball that squishes between your fingers. Once you've done this a number of times, the visual cues alone may be enough to tell you that the syrup is ready. This process takes about 10 minutes. When the syrup is almost done, check to see that your egg whites are at soft peaks. (If the egg whites reach soft peaks before the syrup is done, turn the mixer down to low while the syrup finishes cooking.) With the mixer running at high speed, pour the hot sugar syrup down the side of the bowl, being careful not to let it splash out onto the whisk attachment (or it will be flung everywhere). Whip until the meringue is glossy and mostly cool, another 10 minutes. This is something you will want to do in a stand mixer. Holding a hand mixer this long can be difficult. Once the meringue is no longer hot, you can add in your butter, about 1 T at a time, until the mixture emulsifies and looks like a smooth, shiny icing.
Some flavor suggestions:
Coffee-1 T instant espresso in 1/2 T warm water
Lemon-1 fl oz strained lemon juice or 1 T curd
Orange-1 fl oz OJ or Grand Marnier or 1 T curd
Liqueur-1 fl oz liqueur (Kirsch, Framboise, Rum)
Praline-3 oz praline paste
Nuts-4 oz toasted finely chopped nuts & 1 oz complimentary alcohol (optional)