Normandy Cheese and Onion Tart with Mustard and Tarragon

Although this classic savoury French tart originates from the Alsace region in France, this version is inspired by a misty autumnal day spent picking apples in Normandy before crisscrossing the Suisse Normande – a wild, hilly stretch of the Orne valley just to the south of Caen – in search of a bottle of aged…