The first thing you learn when visiting southwest France is that it’s not quite French. Walk into a café out in the country, you might hear Occitan, a language roughly equidistant between French and Catalan. Look at a road sign, and you will instantly get lost, because place names in this part of France look like they’re written in Celtic. However, wine is an international language, and in Pacherenc, growers use Gros- and Petit Manseng to make pure magic that anyone can understand. Christine Dupuy of Domaine Labranche Laffont makes brilliant red wines under the Madiran appellation, but her white wines might be the real treasure.