1.Preheat oven to 180°C (160°C fan-forced). Line 12-hole (⅓-cup/80ml) muffin pan with paper patty cases. Make cake according to directions on packet, pour ¼ cup of mixture into each hole; bake in oven about 20 minutes. Stand cakes in pan 5 minutes; turn onto wire rack to cool.
2.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.
3.Tint butter cream with pink colouring; spread over patty cakes. Position gum balls on cakes for shells; position Runts for tails. Position Oompas for heads; position spearmint leaves for flippers. Using black decorating gel, dot spots on shells; using red decorating gel, dot eyes on turtles.