What "kitchen" is Joe referring to?

Question

In Mank (2020), Joe calls Mank, who is being massaged by a lady.

Joe: I hear you're hunting dangerous game. Word on the street is radio's golden boy wants to go toe-to-toe with Willie Hearst, and you're helping in the kitchen.

“Radio boy” refers to Welles, who — before Citizen Kane — made a name for himself as a radio and theater actor-director in his 20s.

What "kitchen" is Joe referring to?

Answer 1

Joe is mixing metaphors here, with phrases like:

• Hunting dangerous game
• Going toe-to-toe
• Helping in the kitchen

He's explaining that Welles and Mank are going to make a movie clearly based on William Randolph Hearst (Citizen Kane) and that this is dangerous because Hearst is a powerful man. The phrase "helping in the kitchen" appears to just imply that Mank is helping with the project, almost "cooking up the project" with Welles.