For quite a long time, I’ ve been also making jewellery out of polymer clay. I started with simple yet popular designs before going to more complex objects. One of these simple(r) forms was the cake.
It is really easy to make a polymer clay cake, because you practically have to make 3 (or more) circles and cover them with a solid layer. The decoration is up to you, I made tiny roses on my “chocolate covered strawberry-vanilla cake”. You can find plenty of videos on youtube that explain it quite well.
Actually, with this method, you make a whole cake and you can slice it. Two slices ended up as earrings, and I kep one for myself as a ring. I attached it to a ring base with hot glue and so far it is perfectly water resistant (although not pocket-safe.) It’s really cute, though.