The piping method
You’ll need buttercream icing, a pastry bag, a large star tip and a rubber spatula.
First you need to get the icing into the pastry bag. Here’s how:
Attach the pastry tip to the bottom of the pastry bag. Set the bag over a tall glass or measuring jug, and fold down a cuff. Use the spatula to scoop icing from the bowl into the bag. Fill the bag no more than two-thirds full or else icing will squirt out of the top. Lift the bag out of the glass and twist the top to close it. You can hold the bag closed by keeping the twisted end under the palm of your hand while you pipe.
To pipe on icing:
Set the cupcake on a flat surface instead of holding it in your hand. Start by piping a circle around the outer edge of the cupcake. Continue the coiling motion until you reach the centre of the cupcake. To finish off, stop squeezing the pastry bag, and then pull the tip up while twisting your wrist to get a swirl on the top.
If you have to ice a lot of cupcakes, this is the fastest way to ice them: Place them on a baking tray in neat rows. Start piping from left to right on the centre row, then continue to the next. Then, rotate the tray so the next rows are closer to you, and start again from the centre row.