The ChefWatson API is marked experimental in the documentation you linked above. Experimental services can be found in the Bluemix Labs Catalog.
Experimental services often do not make it to Beta (let alone GA) but they are placed in the labs catalog so that users can play with them and the product teams can gather usage metrics.
My best guess is that the ChefWatson API has since been removed from the labs catalog and is no longer available.
You might be able to achieve some of what you're trying to do by interrogating the API hosted for https://www.ibmchefwatson.com/
It requires you to understand the ingredient IDs (I couldn't find a list) but after you've got that you can return matches for that ingredient.
As an example - the results for the ingredient 'chicken' can be found like so:
https://www.ibmchefwatson.com/IronChefUI/jaxrs/recipe/tuples?q&ingredientid=1154