ABANDONED. Science fiction short story about a food that if you eat only it, you live forever.

[Korvin]

I remember reading a science fiction short story about a food that, if you eat only it, you live forever. It may have been part of a collection of short stories. It was about a new up and coming restaurant owner who gets invited to an old guys house for supper. He is served a bowl of grey mush by the butler. It looks unappetizing but tastes amazing. The host simply wolfs down his bowl. As they are talking, he reveals that is is actually much older than he seems. Apparently, if you eat only this grey mush you live forever. Now he is ready to die/start eating other food. His butler is the one who knows the recipe and how to prepare it. So now he is looking for 'new employment'. The butler's father is the one who created the recipe. He was a cook in a french king's kitchen. However, he slept with the queen and was killed, but not before he told his son the recipe. The son/butler is actually hundreds of years old. In the end, the restaurant owner hires the butler and gives him what he always wanted. He is now in charge of a large staff, a big kitchen and has virtually an unlimited budget. They sell little jars of grey mush.

I would like to find this story again, so if anyone knows the name of it or which anthology it's part of, I'd appreciate it.

[Kris]

Korvin, around what year did you read this book? A range of years is fine.

Did you read this short story in a sci fi or fantasy anthology? (What was the common theme? One or multiple authors?)

[Kris]

No response, moving to Abandoned folder.

Korvin (OP) was last active on the site in June 2020.