He would go so far as to say that they are the secret ingredient of his success.
"They just have to ask for a special shape, with a secret ingredient."
"Could there be a secret ingredient in the wood that will make me normal again?"
Here is a report on how it went, and a "secret ingredient" that may have helped.
"That is the secret ingredient, the best flavor in the world."
As they return, secret ingredients are getting a contemporary spin.
But not, he hoped, on this job - if his secret ingredient worked.
At the start, each artist will be given a secret ingredient.
I also learned about a "secret ingredient" that seems to help my body dump water.
The secret natural ingredient, chocolate, has a lot of hidden health benefits.