Preheat the oven to 180°C/Fan 160°C/Gas Mark 4. Line a 12-hole muffin tin with paper cases.

Measure all of the muffin ingredients into a free-standing electric mixer and whisk until blended. Spoon the mixture equally between the prepared paper cases.

Bake in the preheated oven for about 20-25 minutes until well-risen and lightly golden on top, and the muffins spring back when lightly pressed with a finger. Remove the muffins from the tin and leave on a wire rack to cool completely.

Meanwhile, colour half of the ready-to-roll icing green and the other half brown. Roll out the green icing and shape into 12 leaves. Use a toothpick or cocktail stick to draw the veins on the leaves. Shape the brown icing into 12 stalks.

Colour the buttercream orange using the orange food colouring and spread the icing over the muffins. Decorate each one with eyes, a nose and mouth using the chocolate-flavoured writing icing and then finish off by adding on the leaves and stalks.