It can't be their cooking skill. Why do you think Bruce Wayne keeps Alfred on staff? It's because Bruce can't cook an omelette for his life. Not true of Julia Child:
No, to determine how the Caped Crusader and the French Chef are similar we have to delve back into her WWII origin. Or, as Wikipedia has it (and doesn't Wikipedia have it!):
...after the bombing of Pearl Harbor in 1941, [Child] joined the Office of Strategic Services (OSS) after being turned down by the United States Navy for being too tall.Yes, you read that right.
She started out at OSS Headquarters in Washington, working directly for General William J. Donovan, the leader of OSS. Working as a research assistant in the Secret Intelligence division, Julia typed up thousands of names on white note cards used to keep track of officers.
For a year, she worked at the OSS Emergency Sea Rescue Equipment Section in Washington, D.C., where she was a file clerk and also helped in the development of a shark repellent to ensure that sharks would not explode ordnance targeting German U-boats.