Preheat oven to 160°C/320°F. Spray a 24cm square cake tin with oil spray. In a bowl place raisins and add orange zest and juice. Set aside while preparing cake mixture.
Place flours in a bowl with baking soda, cinnamon and 1 teaspoon baking powder. And mixed spice.
Whisk egg yolks until pale and creamy. Whisk in sugar and then oil, half at a time. Fold in dry ingredients half at a time.
Fold in carrots, raisins and juice and bananas half at a time. Whisk egg whites until soft peaks form.
Carefully fold into carrot mix with the remaining baking powder. SPoon into prepared tin and bake for 45 minutes to 1 hour or until firm to touch.
To make icing, mix cheeses icing sugar and orange juice together until smooth. Spread over cooled sponge. Cut in squares.