Mix the ingredients for the dough / crumble into a dough. Line a baking sheet (the higher drip pan) with parchment paper - grease the sides with butter.
Place half of the dough on the baking sheet (crumble) and press down. It is best to roll over it with a rolling pin or a glass.
Mix all ingredients for the topping (except the mandarins) with the mixer. Finally, add the mandarins and also mix in with the mixer (the mandarins are peeled apart, but that`s how it should be). Put the topping on the dough. Crumble the remaining dough on top as a crumble. Bake at 175 degrees for 1 hour and let cool in the mold!
It is best to bake the cake the day before and let it cool completely overnight in a cool place.