For 10 people.
This is the traditional French Christmas cake.
With a wooden spoon beat a mixture of 4 yolks of egg and 4 tablespoonfuls of caster sugar.
When it is pale straw colour and frothy stir in very gradually 7 or 8 tablespoonfuls of flour, and finally fold in the whites of the 4 eggs, very stiffly beaten.
Spread this mixture about 1/2" deep in a tray lined with greaseproof paper such as is used for Swiss rolls.
Put into a moderate oven, but don't let it get dry.
Lift out; and moisten the paper to make it easy to remove.
Whilst the sponge cake is still warm, spread it with jam or cream, and roll up just like a Swiss roll.
Wrap it fairly tightly in some more greaseproof paper, and leave it in a cool place for 24 hours.
Then spread a thick coffee or chocolate butter cream all over it.