To shell the nuts
Spread the nuts on a baking tray.
Roast for approx. 8 mins. in the centre of an oven preheated to 200 °C until the shells crack open. Remove from the oven, rub the nuts gently with a damp towel until all the shells have been removed. Coarsely chop the nuts.
Place the butter in a bowl, whisk in the sugar and salt. Add the egg yolks and continue to whisk until the mixture becomes lighter in colour. Combine the chopped and ground nuts, flour, baking powder and chocolate, stir into the mixture. Beat the egg whites with the salt until stiff, carefully fold into the mixture using a rubber spatula. Transfer the sponge mixture to the prepared tin.
Approx. 50 mins. in the lower half of an oven preheated to 180°C. Remove the cake from the oven, allow to cool slightly, remove from the tin and leave to cool on a rack.