OK recipe courtesy of Delia Smith. I didn't make it to use on a Christmas cake so I make one third quantity which was enough. I used 1 egg and 1 egg yolk, and a splash of almond essence, a slightly larger splash of lemon juice. The only brandy I could find in the house was apricot brandy so a largish splash of that went in too!
Almond Icing (Marzipan)
Ideally, before you cover your cake with royal icing, almond icing should be left for several days after it has been applied to the cake, to dry out its oiliness. But if you find you don't have the time for that, then I suggest you top it with the rough 'snow' icing (see Royal Icing recipe) which is thick enough for the almond oil not to discolour it. If you wish to use ready-made almond icing (marzipan) you will need a 1½ lb (700 g) quantity to cover a 7 inch (18 cm) square cake.
For a 7 inch (18 cm) square or an 8 inch (20 cm) round cake
Ingredients
12 oz (350 g) ground almonds
6 oz (175 g) icing sugar plus extra for dusting
6 oz (175 g) caster sugar
3 large eggs, one of them separated
½ teaspoon pure almond extract
1 teaspoon lemon juice
1 teaspoon brandy
Begin by sifting the icing and caster sugar into a large bowl, then stir in the whole eggs and the egg yolk. Place the bowl over a pan of barely simmering water and whisk for about 12 minutes until the mixture is thick and fluffy. Then remove the bowl from the heat and sit the base in a couple of inches of cold water. Whisk in the almond extract, lemon juice and brandy and continue to whisk until the mixture is cool. At this point stir in the ground almonds and knead to form a firm paste.
Now divide the paste by cutting off one-third of it. Dust a working surface with icing sugar and roll the smaller piece of paste into an 8 inch (20 cm) square (you can either use a ruler for this or else the base of the cake tin as a guide). Next brush the top of the cake all over with egg white, then turn it upside down and place it centrally on the rolled-out almond paste. Using a palette knife, press the edges of the paste up all round the edges of the cake, then turn the cake the right way up to deal with the sides.
Once again dust the working surface with icing sugar, and roll out the rest of the paste into a length 14 x 6 inches (35 x 15 cm). Divide this in half lengthways, then brush the sides of the cake with egg white and fix the two strips of almond paste all around the sides ? you can smooth over the joins, first with a knife then with a rolling pin. Now leave the cake, covered with a clean cloth, for as long as possible up to seven days.