The quote indeed does not have a verb, but there is an implied "This is a" and so "is" would be the verb. The sentence before this is:
Wife kills husband with leg of lamb, then disposes of the weapon by feeding it to the cops
The first clause also has deleted "the" from in front of "wife" and "husband", as well as "a" in front of leg of lamb.
This deletion of some grammatical elements is stylistic
Offering here is sort of a euphemistic use.
from Merriam Webster:
1a : the act of one who offers
1b : something offered
especially : a sacrifice ceremonially offered as a part of worship
1c : a contribution to the support of a church
2 : something offered for sale or patronage
"latest offerings of the leading novelists"
Looking at the definition 2, this is exactly the usage that is mentioned in your quote. It is referring to the Roald Dahl's story "Lamb to the Slaughter".
Since Dahl wrote this story to sell and be read by people, he "offered" it to the public, and so it is an "offering"