Beat together the butter and icing sugar using a wooden spoon or electric mixer.
Add the plain flour and mix until it forms a dough.
Wrap the dough in cling film and place in the fridge for 15-30 minutes.
Preheat the oven to Gas Mark 4 or 180 degrees and line two baking sheets with baking paper.
On a floured surface, roll out the biscuit dough and use a smooth circular cutter to cut out your biscuit shapes. In every other circle, I cut out a heart using a small cutter (for the tops).
Bake in the oven for 10-12 minutes or until all of the biscuits are starting to look golden.
Place the biscuits onto a wire rack to cool.
Make up a large bowl of icing by gradually adding water to the icing sugar. The icing needs to have a thick consistency to ensure it covers the biscuit.
Separate the icing into smaller bowls and mix a selection of colours. For authentic party rings you will need yellow, blue, pink and white. To make the purple, I mixed together the leftover blue and pink icing.
Dip each biscuit into the coloured icing, and set aside. As the icing just begins to dry, drizzle straight lines of another colour (for example, dip into pink, then add lines of yellow icing). Feather these using a cocktail stick or cake tester and leave to set on a wire rack.
Repeat this with the different colours until all of the biscuits are iced. Leave to set (an hour or so) then serve and enjoy!