Mix the butter, sugar, vanilla sugar and salt until frothy. Stir in the crème fraîche, add the eggs one by one, stir for another 5 minutes. Sift the flour or stir with a whisk so that it is nice and airy and mix with baking powder. Carefully add the mixture together with the milk to the cream. Melt the dark chocolate either in a double boiler or in the microwave. With the latter method you have to be careful that nothing burns. Allow to cool slightly. Pour 1/3 of the dough into a second mixing bowl, stir in chocolate, cocoa powder, amaretto and oil.
Grease a cup cake mold, layer the light and dark cake dough alternately and then carefully mix both types of dough with a fork to form a marble-like pattern.
Oven at 175 ° C convection - 60-75 minutes (make a test with the knitting needle)
Variation: 3 P. omit vanilla sugar. Instead of the milk, add 5 cl egg liqueur to the light-colored batter.