With a handheld or stand mixer, beat the butter for 2-3 mins until pale and fluffy
Add half the icing sugar and beat again until combined. Repeat for rest of the icing sugar
Add the milk and mix for 5 mins
Divide the buttercream equally in two and to one half add the cocoa powder and mix until combined. Add your black gel food colouring and mix until evenly distributed
With the remaining half, split this into 3 and colour with the blue, pink and orange gel food colouring
Once the buttercream is coloured, get a large piece of cling film and place it down flat on a hard surface
Onto the cling film, add long rows of the different coloured buttercream, making sure each row is touching along their length. We used the following pattern: black, pink, black, blue, black, orange
Next, roll the cling film up so the two end rows of buttercream meet and twist the cling film at each end
Prepare a piping bag with your piping tip
Snip one end of the cling film and place this end first into the piping bag
Squeeze the buttercream down to the tip and begin piping on top of the cupcakes
Add some edible silver glitter and enjoy!