It’s not traditional. Also it’s not similar to the pic. It was invented in the 1970s by a French Chef. The technique involves “vacuum sealed” ingredients, ensuring there is no air between the ingredient and water. Water is kept at a constant temperature, much lower than usual cooking temperature, and the ingredients are cooked for a very long time.

End result is an evenly cooked ingredient with full moisture content. But there won’t be any browning (Maillard reaction), which is key in many recipes.