Some people do not like to make homemade buttercream frosting and they should buy a couple of containers of pre-made buttercream frosting at the store (vanilla or butter flavor).
German buttercream frosting is very rich but not as sweet. It consists of vanilla pudding carefully stirred together with equal amounts of butter until fluffy. The butter and the pudding must have the same temperature to meld together or it will not work. Here, the butter is beaten first, then the pudding is added a spoonful at a time until well blended.
The recipe here for Frankfurter Kranz uses one, small packet of pudding and one stick of butter. You will need to double that amount, at least, for a regular-sized cake.
Go to Recipe for small Frankfurter Kranz as seen in the pictures.