Parson's Tale 31 ff. Everything good comes from God. What may be bad comes from lack of skill or knowledge. He does not repent of translating Boethius, even though it is clearly a fictive dialogue that includes passages of poetry. Also is the Wife of Bath's tale about the relationship between gentility and promise-keeping.
Cooks turn substance into accidence by disguising food so that it is appetizing.
They do this in response to the glutton's desire for more and tastier food. The line could also be used of those who write fiction.