How to make royal icing

You will need:

• 4 large free-range egg whites
• 900g icing sugar
• ½ tsp glycerine
• 1 drop of blue food colouring (optional)

1. Put the egg whites in a mixing bowl. Sift out the icing sugar.

2. Carefully stir in the egg whites, a little at a time, until the mixture reaches a thick dropping consistency. Start whisking the mixture until it starts to form soft peaks (this will take 10-15 minutes if using a balloon whisk), then stir in the glycerine (from the baking aisle in large supermarkets).

3. If you like, stir in 1 drop of blue food colouring to make your icing extra white.

4. Use a palette knife to spread the icing over your marzipan-covered cake, then leave to set.