Cream the butter in the bowl of a stand mixer fitted with a paddle attachment on medium speed.
Gradually add the powdered sugar, and beat on low speed. Mix until the sugar and butter are combined.
Add the pure vanilla extract and the salt to the frosting mixture. Continue to mix on medium-high speed until the frosting becomes smooth.
Add the milk to adjust the thickness of the frosting. If you desire a thinner consistency, add more milk, 1 tablespoon at a time. If the frosting becomes too thin, simply add more powdered sugar.
The frosting can be used to frost a 9-by-13-inch cake, to coat the sides of an 8- or 9-inch layer cake, or to top 12 cupcakes. Make sure the cake is completely cool before attempting to coat it with frosting.
You can make this frosting the day before you use it and store it in an airtight container in the refrigerator. Stir the frosting before applying it to a cake.
American buttercream is a creamy and smooth classic. It's most commonly enjoyed on cakes, since it's one of the easiest and quickest buttercreams to prepare. It also holds up reasonably well at room temperature and is an excellent buttercream for decorating and piping. American buttercream is simple to customize with gel colorings and extracts.
American buttercream is a fantastic base for other flavors. You can easily change the taste by adding a flavor extract such as almond extract, orange extract, or peppermint extract. If you'd like to try something more adventurous, you could make cream cheese frosting, peanut butter frosting, or chocolate frosting by adding just a few ingredients.
Ermine is prepared on the stove by whipping cooked flour into butter and granulated sugar. Ermine buttercream is light with a custard-like texture. It's less sweet than American buttercream, and it's not as resistant to warm temperatures, making it a poor choice for decorating and piping. Ermine was the original frosting for red velvet cake; you can find this old-fashioned combination in our recipe here.
Swiss meringue buttercream is prepared by whisking egg whites and granulated sugar in a bowl on top of a saucepan of boiling water. The egg whites are removed from the heat and then beaten until stiff peaks form. Finally, butter and other flavorings are added.
Swiss meringue buttercream is exceptionally light and creamy in texture and less sweet than traditional American buttercream. Swiss meringue buttercream is commonly used as a filling for French macarons to balance the sweetness of the macaron shells.
Italian meringue buttercream is almost identical to Swiss meringue buttercream in regard to taste and texture. Italian meringue buttercream is also prepared the same way except for one difference: a sugar syrup is added when the egg whites are being whipped into a meringue. Italian meringue is light and silky, but it holds its shape very well, making it perfect for decorating and piping.
French buttercream is prepared by whisking egg yolks and sugar syrup together. The egg mixture is then combined with butter and other flavorings to make a light, yet rich buttercream. French buttercream is better for filling desserts than for frosting or piping, since it's not as stable as other buttercreams.
German buttercream is prepared by combining custard and butter with powdered sugar and other flavorings. Since German buttercream is custard-based, it is not recommended for decorating or piping because it can melt quickly. German buttercream is commonly used as a filling because of its rich and creamy texture.
American buttercream is by far the most convenient and straightforward of all the buttercreams on our list. It's a good starting point for anyone beginning to dabble in frosting and decorating their desserts. American buttercream is always bound to be a hit!