here's what I think ...

I think the answer to your problem is very simple...find a muffin pan which is similar in size to the one used by the restaurant. They most likely use a commercial muffin pan which holds a greater quantity and larger size of muffin, so try inquiring at a commercial bakery supply. There is definitely one in New York City which will sell to the public (don't remember the name) and I'm sure that by now, you can find many suppliers on the internet. Also, try culinary suppliers such as Williams Sonoma who sell specialty and high quality cook ware.
I don't think that flower pots are the answer, since it would a be tedious and time consuming process for a restaurant to bake this way.
Good luck! Hope I helped!
PS. I also think that you should ask Sarah, she's a very helpful, generous person.