Mix the first 5 dry ingredients for the layers. Mix 2 tablespoons of this dry mixture with the walnuts and raisins, which will eventually help to evenly distribute the mixture.
Beat the eggs with both sugars into a fluffy cream and gradually add the oil, orange juice and zest. Add the dry mixture to the liquid ingredients and homogenize.
Then stir in the carrots and finally raisins and walnuts. Place the mixture into a buttered form, covered with baking paper. Put the carrot cake layer in to bake in a preheated 356°F (180 °C) oven for about 60 minutes, but keep an eye on it and finally check it with a toothpick.
Leave the baked cake layer aside to cool and put on a tray to cool completely. Then cut it into 2 separate layers.
For the cream, first whip the butter to fluffiness. Add the cream cheese, orange zest, and gradually mix in the powdered sugar. Whisk into a smooth cream, but do not overdo it, in order not to liquefy the cream.
Put the cream briefly in a refrigerator. Then stick the layers together with the cream and smear the top with the remaining cream. Make an appropriate decoration and let the cake cool for several hours before serving.