Fimo is a polymer clay, a little bit like playdoh but firmer and less sticky. It hardens in the oven when cooked for several hours at 130°C, depending on the thickness of your clay. I tested it with va thumbnail to see if I could still mark it.
You can build up your burgers as you would with the real ingredients. The lettuce was made by cutting shards off a block of green fimo with a sharp knife. The red onions were made by rolling up purple and white clay and then cutting slices. I'm particularly proud of them.
You can add texture using a sharp knife or some scrunched up tin foil. I bought a beginner Fimo kit from eBay and it came with some wooden texturing tools.
To make the bread look more toasted, dust the top with glitter colour powder.
You can attach the jewellery O rings straight to the fimo before cooking. If you are making beads made sure you put BIG holes into your clay.: I found it impossible to pull metal wire out.
If you want to make something a bit more fancy, you can combine the fimo with doll's house miniature crockery for a fabulous afternoon tea. The fimo will stick to the ceramic or metal while it is heated and you can add the O rings afterwards using super glue or apoxy.
To make tea or other transparent things use liquid fimo. You can colour it using powdered colours and it bakes in the same way as the normal clay. That's how the tea and the jam was made. It is very sticky and does no flow easily once mixed. I had to dab it on using a chopstick.
Don't forget to glaze your creations once they are baked to protect them. You can get both satin and matt glazes. Some websites say use several coats but I've found one works fine.
You rip what you sew!