Carol Foster's iced rainbow bars

Preheat a moderate oven to 180ºC or 350ºF. Cream fat and sugar until creamy and fluffy. Whisk eggs well then add eggs well whisked bit by bit to creamed fat and sugar. Beating well in each addition. If the mixture starts to curdle, add some flour. Sift flour and salt to the mixture and stir lightly. Keep stirring until the mixture reaches a dropping consistency adding a little water if necessary. Once the mixture has reached a dropping consistency, divide the mixture equally into different bowls (depending on how many colours you want your cake to have). Add drops of food colouring and coco powder to your bowls of cake mixture. Pour the different colours of cake mixture in a prepared 8 inch tin. Bake in a moderate oven for 40-45 mins. When the cake has cooled, cut into rectangles then ice however desired.