For the biscuits ...
220g butter, softened
200g caster sugar
2 tsp vanilla extract (or other extract of your choice)
1 large egg
425g plain flour
Cream together the butter and sugar, add egg and extract, then sift in the flour and combine into a smooth dough. These biscuits will take about 8-10 mins to cook at 180C depending on their size.
We mixed up runny icing by combining icing sugar and hot water, then coloured it using food colouring paste. Then we painted it on to our biscuits with small, clean paintbrushes. We found that we got the best results by covering our biscuits with a pale colour first, then while it was still runny adding tiny amounts of the darker colours where we wanted then.