The most important thing for this dessert is to prepare the 2 separate mixtures, brown and white, by using the exact quantities of the ingredients.
Start with the brown mixture. Melt 1 1/3 tbsp (20 g) of butter and the chocolate in a water bath and add the oil. In the meantime, beat the remaining products for the brown mixture in a bowl until you get a homogeneous mixture. Finally, add the melted chocolate and stir well.
Prepare the white mixture the same way. Once they're both ready. smear 2 aluminum forms well with butter. First, put 2 tbsp of the brown mixture, to cover the forms, then a tbsp of the white one and continue in this order.
Bake the chocolate gateau 6-7 min. in a preheated 428°F (220 °C) oven.