Buttercream can be made with varying techniques. As an American baker the American Buttercream or (ABC) is quite common. But not all buttercream is created equal. ABC can be very sweet. Here is a simple breakdown of some common buttercream types:
AMERICAN: Powdered sugar + butter + milk/cream (or water) +some variations may also have shortening
American Buttercream is easy and fast to make but it can be overly sweet, gritty texture or greasy due to its fat content, particularly when made with shortening.It does however stay relatively stable in warmer climates and is not as easily perishable as variations with eggs.
SWISS: Egg whites + Sugar syrup + butter
Swiss Meringue Buttercream (SMBC) has a smooth texture but requires more time and attention to techniques. In this method, egg whites and sugar are cooked over a Bain Marie (double boiler). Once the sugar has dissolved and reaches the appropriate temperature it’s whipped into meringue until stiff peaks form. Butter is then added and whipped until well incorporated. More care must be taken in warmer environments.
GERMAN: milk+ sugar + egg yolks + cornstarch
German Buttercream is a cooked custard/pastry cream base with butter. It is smooth and rich. It will have a yellow tint as it has the custard/ egg yolk base so it will not be bright white as in some other buttercreams.
FRENCH: Egg yolks + sugar syrup + butter
French Buttercream is similar to Swiss Meringue but has a richer taste as it is made with egg yolks. French Buttercream is easy to pipe and smooth.
ITALIAN: Sugar syrup + egg whites + butter
Italian (IMBC) are made with combining components of sugar syrup into a soft ball stage then added to egg whites to form a meringue. Butter is then added and the ingredients are incorporated. Care must be taken to preserve the state of the meringue. This buttercream is very smooth such as the other meringues but may have a bit more stability as it is prepared at a higher temperature.
WHIPPED TOPPING/FROSTING: heavy cream + sugar + stabilizer (such as gelatin)
This is not a buttercream at all but is a whipped cream topping that can be added to many desserts. Stabilizing agents such as gelatin can be added in order to prevent it from breakdown. It is light and pairs well with lighter cake bases and berries.
CREAM CHEESE: cream cheese + powdered sugar + cream
A rich frosting typically paired with red velvet cakes and is softer than ABC. This type of frosting is not as stable and will not hold up as well in warmer environments.