1.Preheat oven to 180°C; grease and line deep 26cm x 36cm baking dish.
2.Make cake according to directions on packets, pour into pan; bake about 1 hour. Stand cake in pan 10 minutes; turn onto wire rack to cool. Using serrated knife, level cake top.
3.Turn cake cut-side down. Using picture as a guide, cut out stella stegosaur’s shape. Position cake on 35 x 45cm prepared rectangular board cut-side down.
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 green colouring; spread all over cake.
6.Cut After Dinner Mints in half diagonally; place mints along cake body so they are raised along the diagonal cut to look like armoured-plated spikes.
7.Cut mint sticks in graduated lengths; place in position along back so they follow the line of the spikes, longer in the centre, and shorter at the sides.
8.Starting at the tail, cover body and legs with slightly overlapping spearmint leaves. Using a sharp knife, cut about 10 mint leaves in half horizontally; place in position around neck.
9.To decorate face and feet, use Tic Tacs for claws, a thin piece of raspberry strap for mouth and a mint stick, thinly sliced, for eye and nose.