Cream butter and sugar together until light and fluffy.
Use a fork to gently flatten (dip the fork into some plain flour every now and then to prevent it from sticking to the biscuit).
While many choose to join their Yo Yo's together with a butter icing, we always made a simple icing using icing sugar, a small piece of butter, probably about half to one teaspoonful, a little vanilla, and just enough boiling water to mix to a nice consistency.