CAN ONE USE ROYAL ICING ON A BIRTHDAY CAKE? I AM PLANNING ON BAKING A HELLO KITTY BIRTHDAY CAKE FOR MY DAUGHTER, WHICH MEANS THE ICING MUST BE VERY WHITE. WE DON'T LIKE THE TASTE OF READY TO ROLL FONDANT ICING AND BUTTER ICING'S COLOUR IS TOO YELLOW. I ALSO WANT THE ICING TO HAVE A VERY SMOOTH SURFACE. I ONCE SAW NIGELLA MAKING ROYAL ICING FOR CUPCAKES, WHICH IS EXACTLY THE "LOOK" I WANT FROM MY ICING, BUT FROM INFO GATHERED ON THE NET I UNDERSTAND THAT ROYAL ICING IS QUITE HARD WHEN SET. NOT SURE IF THIS WOULD BE VERY TASTY ON A LARGE CAKE. ANY OTHER SUGGESTIONS?
Royal icing can set very hard when it dries out, though how hard it becomes will to an extent depend on the conditions it is being stored in - if it is very warm and humid then the icing will not necessarily dry out completely. You can also soften royal icing slightly by adding some liquid glycerine to your royal icing mixture - 1 teaspoon of glycerine per 450g/1 pound of icing (confectioners') sugar. As glycerine is an invert sugar it will tend to attract water and so prevents the icing from drying completely, ensuring it stays slightly soft. If the cake is for smaller children then you may prefer to use pasteurized egg white or dried egg white rather than fresh egg white, to reduce the risk of salmonella.
Royal icing can be flavoured but make sure that any flavouring used is a clear liquid as otherwise it will tint the icing. Lemon juice is popular as the sharpness slightly offsets the sweetness of the sugar and the lemon juice can help to give a very white icing. Many flavourings can be bought in this form though for vanilla it will tend to be a synthetic manufactured vanilla rather than a natural vanilla extract. You can also buy liquid whitener which will brighten up a slightly off-white icing - Wilton is a good brand to try. Unfortunately though it is not suitable for trying to whiten a butter-based icing or frosting. Any flavourings or whiteners need to be counted as part of the liquid added to the icing sugar, otherwise the royal icing can become too thin.
Royal icing is very sweet so it will taste similar to ready to roll fondant icing. If you remain worried that this will not be the icing for you then you can try out a small quantity on a cupcake or smaller cake before deciding. Another type of frosting to look at is one commonly called "seven-minute frosting" which is a little less sweet than royal icing. This icing is made by whisking egg whites and sugar over a saucepan of simmering water for 7 minutes until it is very fluffy and spreadable. It can then be spread over a cake and smoothed with a palette knife or thin spatula, though it will be difficult to get a super-smooth finish to the surface. Again for smaller children it would be advisable to use pasteurized egg white (which can be bought in cartons in the chilled section of some supermarkets) for this icing.