1.Preheat oven to 180°C (160°C fan-forced); grease and line two 15cm x 25cm loaf pans and deep 22cm-round cake pan. Make cakes according to directions on packets, evenly divide two-thirds of the mixture between two prepared loaf pans. Spread remaining mixture into prepared round cake pan; bake round cake pan in oven 30 minutes and loaf pans 40 minutes. Stand cakes in pans 5 minutes; turn onto wire racks to cool. Using serrated knife, level cake tops so they are the same height.
2.Turn cakes cut-side down. Using paper pattern from pattern sheet, carefully cut out platypus. Using left-over cake, shape into four feet. Assemble cakes on prepared board, cut-side down.
3.To make butter cream; beat butter until white as possible, gradually beat in half the sifted icing sugar then milk, then remaining icing sugar. Beat until smooth.
4.Tint a quarter of the chocolate butter cream with black colouring. Spread black butter cream over bill. Spread remaining chocolate butter cream over body, roughen with a fork.
5.Mark nostrils and mouth in bill.
6.Cut marshmallow in half horizontally; using a little butter cream, attach one chocolate mint round to each marshmallow half for eyes, position on cake.
7.Cut claws from licorice strap; position on cake.
Use toothpicks to position paper pattern on cakes, ready to cut out. Assemble cake on prepared board ready for icing.Note