I have made them using can foam spray you use to fill cracks with. From the hardware store. Takes a little practice to get just right.
Put paper liners in your muffin tin. Shake can then squirt into cups. It does expand as it sits so go slowly.
One can makes about 24.
...talk about your childhood wishes, you can even eat the dishes! "Come inside", said the bird to the mouse. I'll show you what there is in a treathouse. (licensed and inspected home kitchen)