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Whip the butter. Add the sugar. Mix in the cream and salt.
The first step is to change the consistency of the butter so that it becomes light, fluffy, and easy to mix with the other ingredients. Place it in a mixing bowl and beat the butter with a hand mixer or using a stand mixer for several minutes. Continue beating the butter as you add the sugar. Mix until the sugar is fully incorporated into the butter. Finish the icing by beating in the cream and salt until the icing is light, fluffy and fully mixed. Use it to ice your cake or cupcakes immediately, or refrigerate for later use. This icing can be easily altered to make a chocolate buttercream by adding a few tablespoons of cocoa. Add a few drops of lemon juice, almond extract, or another flavoring to match the cake flavor you made. Create a colorful buttercream icing by mixing in a few drops of food coloring.