YOU MAY THINK that someone who spends their professional life tasting dozens of wines a week will have sipped just about everything the world has to offer. It’s true—to a point. But like the art critic who stumbles across a rare masterpiece at auction or the literary critic who discovers the next big thing, there are times when a wine knocks even a critic sideways, surprising with both its flavor and its quality.

This happened to me a few weeks ago. I was handed a white wine at a tasting, and its pale yellow color, floral...