Preheat the oven with electrical heat at 175 degrees Celsius.
Butter a baking form and sprinkle the bread crumbles in the form.
Mix the margarine and the sugar smooth.
Mix the eggs with the margarine and the sugar fluffy and white in color with an electrical mixer.
Pour the flour, baking powder, and the milk in the batter and stir.
Divide the batter in two different bowls. Add the vanilla sugar in one part and the cacao powder in the other.
Pour half of the vanilla batter in the baking form. Pour the cacao batter on top of the white one, and last add the second part of the vanilla batter on top of the cacao batter in the baking form.
Stir a fork in the batter so you will get a marble pattern.
Put the baking form in the lower part of the oven for fifty minutes. Let it cool down for five minutes and put it upside down on a baking paper .