Hi James,
Thanks for the nice review! Although I can't speak specifically about the recipe you used, in general, If you're finding the cookie is too thick for your liking try adding less dough into the cavity of the mold. It doesn't need to be flush all the way to the top of the mold's rim as long as it's even. That will give you a bit more control over the final result. I hope you give it a try again next season. I'd love to hear how it goes!