Preheat the oven to 180 degrees or gas mark 4.
Place all of the ingredients into a large bowl and mix well.
Line a cupcake tin with 12 cases.
Add the cupcake mixture to each cake case until it is ¾ full.
Bake the cupcakes for 20-25 minutes.
Place the cupcakes on a rack to cool and make the icing.
Mix together butter and icing sugar with the zest and juice of half an orange.
Pipe onto the cupcakes and decorate with a sugar carrot (optional).