Wilton cutters and Americolor gel pastes. I really recommend both products! I used the recipe for Nigella's butter cookie (click here) and my first ever batch of real Royal Icing, the recipe for which is below.
4 cups icing sugar, sifted
4 tbsp meringue powder, or Pavlova Magic
6-8 tbsp warm water
Beat ingredients together until stiff peaks form. Add more water if you need it thinner. Allow at least 1/2 hour for Royal Icing to dry before doing more layers/decorations.