Fondant butterflies can be a beautiful way to decorate a cake or individual cupcakes. Fortunately, fondant is easy to work with, even for inexperienced bakers, and will set up nicely. You can use a butterfly-shaped cookie cutter or cut the butterflies freehand with a sharp knife, and you can use any colour you want. Note, however, that these butterflies take a couple of days to dry in a flying shape, so plan accordingly.
Mix the desired food colour into the fondant, kneading it until the colour is evenly dispersed.
Roll the fondant out very thin -- less than 3 mm (1/8 inch).
Cut out butterfly wings, using a biscuit cutter or sharp knife.
Use the craft knife to lightly score a line down the centre of a small piece of cardboard, and bend the cardboard to 45-degree angles. Set the cardboard on a baking tray or other place where it won't be disturbed, and prop the angles up with cotton balls.
Lightly dust the cardboard with cornstarch, and place the fondant butterfly wings on the cardboard pieces, with the centre of the wings lined up with the fold in the cardboard. Allow them to dry.
Mix some black food colouring into a small amount of royal icing. Place it in a piping bag with the thin round decorating tip (size 3 or 4).
Lay out a sheet of waxed paper, and pipe sets of antennae onto the paper. Allow the antennae to dry completely.
Mix desired food colour into another small amount of royal icing. Add to another piping bag, using the thick round decorating tip (size 8 or 9).
Pipe heads and bodies down the centre of the butterfly wings. Allow these to dry as well.
Use a tiny dab of frosting to attach the butterfly antennae to the heads.
Carefully remove the completed butterflies from the cardboard, and place onto your cake or cupcakes.