Beat the egg yolks. Mix together walnuts, sugar, cocoa, essence and candied peel and mix in to the yolks. Beat the egg whites until stiff and fold into the mixture.
Grease a cake tin lightly and sprinkle with bread crumbs.
Pour in the batter and bake in a preheated moderate oven for half an hour, or till a knife inserted in the centre comes out clean.