Sauternes is only made in one area of the world just outside of Bordeaux, France where the climate is perfect. It is made from Semillon, Sauvignon blanc and Muscadelle Grapes and has been made in Bordeaux for hundreds of years. It is only made in years deemed very good otherwise a lower class of normal white wine is made (not sweet).
Grapes develop Botrytis cinerea or “noble rot” on the outside of the grapes due to the climate and heavy morning fog. This dehydrates the grape from the inside until it’s almost like a raisin. When the grapes are finally harvested (long after the normal harvest, very risky) you only get a few drops of juice from each grape. From here, the process is the same as making a standard white wine.
Only very high-end French oak casks are used. Top producers of Sauternes are some of the most expensive bottles of wine ever sold in history. Thomas Jefferson was a well-known enthusiast, he recorded that after tasting a sample from Chateau d’Yquem, George Washington immediately placed an order for 30 dozen bottles.