http://londoneats.wordpress.com/2012/05/15/sachertorte/
For the cake (sponge adapted from Mary Berry’s recipe):
140g plain chocolate
140g butter
115g caster sugar
1/2 teaspoon vanilla extract
2 teaspoons cold espresso
5 eggs, separated
85g ground almonds
55g self-raising flour
For the filling:
300g jar of good apricot jam
For the icing:
175g dark chocolate
15g salted butter
250ml water
75g sugar
To make the cake:
Grease and line a 23cm / 9in cake tin. Preheat the oven to 180°C (350°F).
Melt the chocolate in a bowl set over a saucepan of simmering water. Stir from time to time until it has melted completely, then leave to cool slightly. We want it to be just warm (and not hot).
In a bowl, beat the butter until very soft. Stir in the sugar, and whisk until light and fluffy. Mix in the vanilla and cold coffee. Add the melted chocolate, and mix well – the mixture should be very light and fluffy by now.
Add the egg yolks, one at a time, beating well after each addition. By now, the mixture should be really light and fluffy. Combine the flour and ground almonds in a bowl, then fold this into the chocolate mixture. The mixture will be getting quite thick by now.
In another bowl, beat the egg whites until you have stiff peaks. Add one-third of the egg whites to the chocolate mixture, and mix well – this will loosen the mixture and make it easier to add the rest of the egg whites. Now fold in the next third, then fold in the final third. By the final folding, try to be as gentle as possible to keep as much air as you can in the mixture.
Pour the mixture into the lined cake tin and use a spoon or spatula to smooth the surface. Bake for 45-50 minutes until the cake is risen and the surface springs back when you press lightly (if you press too hard, the cake acquires dimples). Otherwise you can insert a skewer – the cake is done if it comes out clean.
Remove the cake and leave to cool. Cover the top with a clean tea towel – this will capture some of the steam and keep the top of the cake moist.
To add the jam:
Take the cold cake, and cut in half (horizontally, obviously!).
Put the jam into a saucepan with two tablespoons of water. Heat until the jam is runny and just boiling. Pass through a sieve to remove any “bits”, then allow to cool for a moment.
Cover the cut side of the cake with around half the warm jam – it is easiest to pour in into the middle, then spread using a spoon. Put the other half of the cake on top, then pour the rest of the jam on top of the cake. Use a pastry brush to spread the jam all over the top and sides of the cake. Leave until the jam has set.
To make the icing:
Melt the chocolate and butter in a bowl set over a saucepan of simmering water. Stir from time to time until it has melted completely, then leave to cool slightly. We want it to be just warm (and not hot).
In a saucepan, combine the water and sugar. Heat until the mixture reaches the thread stage (107°C). If you don’t have a thermometer, you can test it manually – let a few drops fall into cold water. The syrup will form a “thread” but doesn’t allow you to roll it into a ball. Once you get to this stage, remove the pan from the head, put the base in cold water, and allow it to cool until just warm.
Mix the cooled syrup and cooled (but still molten) chocolate until you have a smooth, glossy icing. Allow it to cool until it is thick but still flows, and pour onto the cake. Smooth over the top, and spread a little of it down the sides to that the whole cake is coated.
Leave the icing to set overnight. The cake is also better if left to sit overnight, so you’ll just need to learn to resist temptation.
If you have a disaster with the icing (either the chocolate “splits” and becomes oily, or it seizes up and becomes grainy), you can save it by boiling four tablespoons double cream, and adding to the icing to form a ganache. Whisk together the warm cream and chocolate icing, and all should be well again.