By Lenn Thompson, Executive Editor As someone who has tasted several vintages worth now, it's almost impossible for me to understand why the Massoud family, owners of Paumanok Vineyards, are the only ones growing and making chenin blanc on Long Island. It ripens and performs consistently in the vineyard, not requiring unique or special treatment — outside of the regular challenges of growing grapes in a maritime climate, of course. The winemaking Massouds, first Charles and now his son Kareem, have been working with the grape long enough to understand how to get the most from it in the cellar…