Wilton's website features an easy buttercream icing recipe. The recipe makes around 2 1/4 cups of icing, and the icing is suitable for cakes, piping borders, flowers and writing.
With an electric mixer, beat 1/2 cup of solid vegetable shortening and 1/2 cup of butter or margarine in a bowl until fluffy. Beat in 1 teaspoon of clear vanilla extract, and gradually add 4 cups of sifted confectioners' sugar one cup at a time while beating well. Slowly add 2 tablespoons of milk, and beat at medium speed until fluffy. For a spreading icing with a thin consistency, add 2 tablespoons of water, light corn syrup or milk. For a pure white icing with a stiff consistency, replace the butter with an additional 1/2 cup of shortening, and add 1/2 teaspoon of no-color butter flavor.
To make an easy chocolate buttercream icing, beat 100 grams of butter with an electric mixer until it's fluffy. Gradually add 2 cups of a sifted soft icing mixture and 1/3 cup of sifted cocoa until they're fully incorporated with the butter. Add 2 tablespoons of milk to make the icing puff up. For a fuller-flavored chocolate icing, use melted chocolate, or add more cocoa to give it a darker appearance.