An easy recipe for chocolate cupcake icing or frosting is Hershey's "Perfectly Chocolate" Chocolate Frosting recipe on Hersheys.com. The recipe calls for butter or margarine, Hershey's Cocoa, powdered sugar, milk and vanilla extract.
To start, melt 1/2 cup, or one stick, of butter or margarine in a pan or microwave. Stir in 2/3 cup of Hershey's Cocoa powder until it is fully combined. Using 3 cups of powdered confectioners' sugar and 1/3 cup of milk, add each in alternation while beating to maintain consistency and even ingredient distribution. If the icing is too thick, add a small amount of milk as necessary. Stir in 1 teaspoon of vanilla extract to finish.
An alternative recipe is to beat one stick of softened unsalted butter until it is creamy and slowly add 3 cups of confectioners' sugar, 1/2 cup of unsweetened cocoa powder and 1/2 teaspoon of salt. Beat until the mixture is smooth and the ingredients are fully distributed throughout the butter. Continue to beat the mixture while adding 2 teaspoons of vanilla extract and 3 tablespoons of heavy milk or cream. Add more powdered confectioners' sugar to thicken the icing to the desired consistency.
To apply the icing to cupcakes, use a baking spatula to spread the icing on top of the cupcake or use a pastry bag to pipe the icing on top of the cupcake.