Sounds like [The Taste of the Dish and the Savor of the Day][1] by John Brunner.

"I found that something brown and nondescript had been dumped on my plate..."

"I had only taken a small forkful; nevertheless, as I rolled it across my tongue, choirs and and flowers burst into bloom and new stars shown in the heavens."

It goes on to describe how the dish provides longevity, but only if it is the sole food consumed, and even its wonderful flavor eventually palls. The narrator convinces another character that he should go back to eating a variety of foods because a long life without good food isn't worth living.

The story ends with the dish being sold commercially.



  [1]: https://www.isfdb.org/cgi-bin/title.cgi?50136