Summarize this article in one sentence.
This is the type of icing many people picture when they think of a classic birthday cake or cupcake topping. It can be made in less than twenty minutes, then spread over the top and sides of any cake to create a delicious, beautiful covering. . The quickest way to soften butter is to place it in a microwave-safe dish and microwave it for 1030 seconds. If you do not have a microwave, simply cut it into small pieces and leave it out on the counter. Either way, continue on once the butter is at room temperature and slightly soft, but not melted. If you will be serving the cake to vegans, replace the butter and whipped cream with a vegetable fat with rich flavor, such as cocoa butter or coconut fat. These tend to melt and solidify more quickly, which can make them difficult to work with. An easier alternative is margarine, but consider improving on its flavor by adding a small amount of melted vegan chocolate, maple syrup, or other strong-flavored ingredient. Put the softened butter in a large bowl and gradually add 3 cups (720mL) powdered sugar while mixing. This will go faster in an electric mixer, but can be done by hand within a few minutes as long as the butter is soft. If using an electric mixer, start at low speed and increase to medium once there is no dry sugar. You can skip this step entirely and still create a tasty, versatile buttercream icing. However, if you wish, you can alter it by stirring in a small amount of additional flavoring. Consider 1 teaspoon (5mL) lemon zest to pair with angel food cake, 1 ounce (30mL) melted, unsweetened chocolate for an even richer icing, or even a tablespoon (15mL) of instant coffee to give a chocolate cake a mocha flavor. Add 2 tablespoons (30mL) whipping cream (or heavy cream) and 1 tsp. (5mL) vanilla or almond extract, then beat with a spoon or mixer until the color and texture are consistent. If it is thick but spreads evenly off a knife, it is ready to be spread onto the cake. Otherwise, troubleshoot with these tips: If the icing is too soft, beat in 2 tbsp. powdered sugar thoroughly. Repeat until the frosting is thick enough to spread. If the icing is solid in places or cracks when you try to spread it, add 1 tbsp. water at a time, stirring thoroughly, until the frosting becomes soft enough to spread.

Summary:
Whip this up quickly for a rich, sweet spread. Soften 1 cup (240mL) butter Mix the butter and sugar together. Add additional flavors (optional). Mix in the remaining ingredients.