1.Preheat oven to 180°C (160°C fan-forced); grease two 22cm savarin pans. Make cakes according to directions on packet; divide mixture between prepared pans. Bake about 20 minutes. Stand cakes in pans 5 minutes; turn onto wire racks to cool.
2.Using a serrated knife, cut half of one cake in half at an angle, not cutting through base; reserve cake piece for snake’s head.
3.Using paper pattern, cut out snake’s head from reserved cake piece.
4.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.
5.Tint butter cream with lemon yellow colouring; spread all cake pieces with butter cream.
6.Assemble cake on board, with the various cake pieces topping one another.
7.Using scissors, cut Roll-Ups into even-size diamond shapes. Decorate snake with diamonds, alternating the different colours.
8.Using black decorating gel, make snake-eye slit shapes on M&M’s for pupils; position eyes on snake. Cut one diamond Roll-Ups shape in half, trim to make snake’s forked tongue; place tongue in position. Using piping gel, pipe on nostrils and mouth.