Last Saturday I had a go at a frosting technique that I’ve seen done but haven’t tried before. I needed to make some cakes for my son’s preschool open day and didn’t have much time because we had only got back from our holiday the night before. I needed something simple and quick that would look really effective so I decided to make some vanilla cupcakes with rainbow frosting.
To make the cupcakes I used my standard recipe, and while they were cooling I started preparing the frosting. I used plain vanilla frosting (recipe here).

You might also like: Rainbow cupcakes tutorial

If you had slightly more time you could always make the Rainbow cupcakes which I made last year to go with the rainbow frosting. They are great fun to do with kids and look fabulous when cut into.

You will need

A disposable piping bag

A large star nozzle

A small flat paint brush

A tall vase / jug to place the piping bag in while preparing it.

Gel food colouring in your chosen colours – for me this was Red, Yellow, Green, Blue and Purple

24 cooled cupcakes

Vanilla frosting (2 x quantities listed)

Method

• Cut the point off the bottom of your disposable piping bag and insert the large star nozzle, making sure the piping bag doesn’t cover the star.
• Place the piping bag inside your vase / jug and fold the top of the bag over the top of the vase. This is to stop the different gel colours touching and mixing inside the bag.
• Using the flat paintbrush paint a stripe of red gel colour up the inside of the piping bag, stopping a few cm before the top.
• Clean the brush thoroughly with water and dry it.
• I had 5 colours and I tried to space them evenly around the piping bag,
  • Imagine the piping bag viewed from above as a clock face.
  • You have already done the red stripe – this becomes 12 o’clock.
  • Paint the yellow at 12 minutes past the hour and clean the brush as before.
  • Remembering to clean the brush between each colour paint the remaining colours at 24, 36 and 48 minutes past the hour.
• Once all the colours have been painted onto the inside of the piping bag carefully spoon in the frosting, trying not to let it touch the sides as it goes in. Fill the bag as full as you can while still being able to twist the top closed. The fewer times you need to refill the bag the better.
• Twist the top of the bag closed and pipe a practice swirl onto a plate. To make the swirl start at the outside and pipe in a continuous spiral towards the centre, using even pressure to squeeze out the frosting. At the centre stop squeesing, hold the bag straight up and push down slightly before lifting away to make the peak of the swirl.  The colours will be very dark at first but become paler after the first few swirls as you can see from the images below.