For the butterflies I used a Wilton cake/cookie cutter and gum paste. Gum paste dries faster than fondant and holds it's shape better. I think it is sturdier that fondant too. I put the antennae on with buttercream frosting and small circle tip in my pastry bag.
The white cake recipe is from http://allrecipes.com/Recipe/Simple-White-Cake/Detail.aspx. I did have to adjust it for altitude. Baking at 7600 feet makes things dry out faster. So I brushed on each layer simple syrup to make the cake moist. I cut each layer in half making four layers total. I used two cups of sugar to 4 cups of water and brought it to a boil. When the sugar was disolved I removed it from the heat and let it cool a bit and then brushed it on. Worked like a charm. I also used blackberry preserves between the top and bottom layer and buttercream icing between the middle layer. I used this site for the buttercream frosting recipe: http://whatscookingamerica.net/PegW/ButtercreamIcing.htm. Once the cake is made and assembled I crumb coated the cake with the buttercream frosting and put it in the fridge overnight. A cold cake makes it easier to wrap in fondant.