The most important thing about making Royal Icing is to have all of the
utensils completely clean and free from grease or oil.
500g (1lb 2oz) icing sugar (approximately)
85g fresh egg whites (roughly 3 medium/large whites)
3 tsp lemon juice - if used - see "Notes"
1 1/2 tsp glycerine - if used - see "Notes"
1. Make sure everything is clean.
2. Sieve the icing sugar if lumpy.
3. Separate the egg whites - make sure there are no bits of shell, blood spots, white stringy bits or any yolk. It’s best to do this one by one then transfer to the main mixing bow (add the lemon juice now if used).
4. Add the sugar to the egg whites and mix on the lowest speed setting for ten minutes - you’ll need to set your timer. Use a “K” beater attachment and not a whisk.
5. Add more of the remaining sugar to get the correct consistency - see "Consistency" - scrape down the bowl and mix for another two/three minutes (add glycerine now if used). You may need to add up to another 50g of icing sugar to get the correct consistency, unfortunately we can't be specific as it depends on many variables - brand of icing sugar, dampness, size of eggs, etc.
6. Cover with a damp cloth if you’re going to use it straight away, or put into a clean tupperware container and pop into the fridge until required.
Hopefully you'll now have a very white and shiny icing. But things can go wrong:
Any grease in the mixture will stop the icing forming correctly and will give a quite sticky, yellowish mixture - I've never found a way of saving it so best to start again with fresh ingredients. Make sure everything is grease free and your eggs are fresh.
Lemon juice v Glycerine - one makes the icing stronger and the other keeps it soft.
The lemon juice is added to strengthen the icing, due to the effect of the citric acid on the egg whites. This is only used when piping Royal Icing, you wouldn’t want to do this when coating a cake.
Glycerine is added to stop the icing drying out completely, if this is left out then you’ll need a jack-hammer to cut through the icing.
You'd never put both into the same icing mix.