Preheat oven to 180 degrees C. Grease and flour a medium sized cake tin (20x30cm).
In a blender or food processor combine the oil, sugar, eggs and carrots. Blend until smooth.
Pour carrot mixture into a bowl and sift in the flour and baking powder. Mix well with a wooden spoon. Pour the cake mixture into the prepared cake tin.
Bake in the preheated oven for 40 minutes. Let cool, remove from tin and ice.
Bring all ingredients to a boil over medium heat, stirring constantly. Lower the heat and cook for another 5 minutes, until the mixture thickens. Allow the icing to cool slightly, then pour over the cooled cake.