Beat the butter and sugar until frothy, gradually add the eggs and stir in. Stir in the sifted flour and milk, mixed with the baking powder. Divide the dough in half, stir in half of the Nutella and the other half of the orange liqueur or mineral water.
Grease a cake tin, sprinkle with breadcrumbs, pour in the light dough, pour the dark dough over it and carefully mix in a spiral with a fork.
Bake in a preheated oven at 175 degrees (top / bottom heat) for about 60 minutes. Let cool down a bit, turn out onto a wire rack and let it cool down.