Cousins Pascal and Francois Cotat are often considered the greatest domaines in Sancerre. Like Boulay, they work principally with the Kimmeridgian limestone soils of Chvavignol. But Cotat wines are very unique; these are incredibly voluptuous, concentrated Sancerres that demand 5 years or more before they are truly ready. And they last and last.
While there's plenty of tingling acid and herbaceous accent in these wines, these are defined by layers of ripe fruit and muscular structures. Really, no other Sancerres are so opulent, and the power is shocking the first time you taste them. And no other producers can pack Kimmeridgian minerality (which is, while quite stony, almost redolent of oyster shells and shrimp tails) quite as densely as the Cotats can.
Between the cousins there are subtle differences. Pascal tends to make the more powerful wines (he has the older vines), while Francois' are more elegant, but it would be easy to confuse one for the other in a blind tasting.