I would like to make the Coconut Cake from How To Be A Domestic Goddess (p23). However, i can't find 'instant royal icing' anywhere. I have seen it online, but as i am making it for a birthday this weekend i cannot wait that long. Could i substitute this for normal royal icing/fondant icing and really mix it up with the Malibu?
Instant royal icing, or royal icing sugar, is sold in packets in many supermarkets the UK (usually in the baking section, alongside the regular icing sugar). It is just a mixture of icing sugar and powdered egg white to which you add water.
You can make a regular royal icing with egg white and icing sugar. Usually you add around 3 egg whites to 500g icing sugar so for the 125g sugar mentioned in the recipe you will need to use just under one egg white (about 1 1/2 talespoons egg white). Whisk the egg white until foamy then beat in the sugar. However this icing does contain uncooked egg so is not suitable for the young, the elderly and people with a comprimised immune system. You can also add powdered egg white to regular icing sugar and then use this mixture as directed in the recipe. For egg white powder you will need around 2 1/2 teaspoons powdered egg white per 125g sugar.
For the US use meringue powder instead of powdered egg white. You need 2 1/2 teaspoons meringue powder to one cup of confectioners' sugar.