Knead the marzipan with the powdered sugar until smooth and pliable.

Pinch off small pieces and roll each into a slightly irregular oval, like a little potato.

Stir the cocoa powder and cinnamon together in a shallow bowl.

Roll each marzipan potato in the cocoa mixture until fully and evenly coated.

Press a few tiny dimples into each one with a toothpick so they look like real potatoes, then chill until firm.