Marzipan Potatoes are a confection, not actual potatoes.
They consist of yellow sponge cake, filled with sweetened whipped cream, covered with a ¼ inch (½ cm) layer of marzipan, and rolled in or sprinkled with cocoa powder. They are about the size of a cupcake.
They really look like potatoes, when made properly.
There are also small ones, just pure balls of marzipan rolled in cocoa powder, with no cake or cream in them.
They used to be easy to find in Eastern European bakeries in New York City in the 1940s to 1960s. Austrians, Czechs, Hungarians, even Danes made them.
Language Notes
In Danish, called “kartoffelkage” — potato cakes.