Preheat oven 180°Place oil, eggs and sugar in bowl beat lightly , add grated carrots ,orange zest and mix all to combine add the flour, bicarbonate of soda, cinnamon ginger and mix again. Try not to overmix . Pour mixture into a greased tin. Bake in oven gas 180° for 30- 35 minutes or more. Insert a skewer in the cake to check if its cooked.Once baked allow to cool then spread topping evenly. Sprinkle chopped nuts and icing sugar.