I should mention this is definitely an industrial bake. I suppose you could halve the quantities but they always get eaten so why bother? Everybody has their own mum's recipe. This is my mother's and therefore, by definition, the best. Don't go doing anything silly, like adding nuts. I concede that adding a handful of broken amaretto biscuits might be acceptable.

Ingredients - makes a lot

400g of dark cooking chocolate
700g of sugar
8 eggs
250g of butter (cubed),
225g of plain flour

Method

Preset the oven to 180°C

Melt the chocolate and butter in a bowl over simmering water (baine marie). Meanwhile gently beat the eggs and sugar, then stir in the melted chocolate followed by the sieved flour. When reasonably smooth (keep the stirring to a minimum) pour into a lined tin and bake for about half an hour or until lightly firm to the touch in the centre of the tray. Try not to overcook.

Cool completely before cutting.