Make 2 circles with the cream colored clay and 1 circle with the white colored clay
Sandwich the white clay in between the cream colored clay
(OPTIONAL) Put wires to make charm in between sandwich. Put one on each half, on opposite sides (see image on next step)
Roll out chocolate colored clay and put thin layer over the 'cake' and 'marshmallow' sandwich
Slice in half
Poke small holes with a pin to make a cake effect on the cake part of the clay. Make sure not to get any holes on the chocolate or marshmallow.
You could also use the rounded top of a pin to make a bumpy, frosting chocolate effect
Bake according to clay packaging directions