NOW that your marzipan has dried nicely it's time to make your Royal Icing and decorate the cake.
1lb of sifted icing sugar (allow a little more depending on size of eggs)
3 egg whites
1 teaspoon of glycerine
Place egg whites in a bowl and gradually add the icing sugar using a whisk. Continue until the mixture is as thick as you want it. Then whisk with an electric whisk for ten minutes until icing stands in stiff peaks (again you can add more icing sugar at this stage, if needed) .
Then stir in glycerine.
Spread the Royal Icing over the cake covering all of the marzipan. Decorate (I used silver balls but there are many edible decorations that can be bought in all colours and sizes) and then wait for Christmas day.
Enjoy, and have a lovely Christmas!