In a bowl beat eggs with sugar to melt the sugar, add the milk and the oil. Flour and cocoa shuffle along to them and add baking powder (vanilla and if dry, if liquid add it at the end). Gradually stirring the dry mixture to the liquid to obtain a homogeneous mixture. Add the chocolate, cut into pieces. Bake in an oven preheated to 180C degrees about 50 minutes in the form size 20 cm and 2 liters volume.