“Good girl, Rosie! That’s a good girl,” exclaims my host, Gareth Renowden. The godfather of New Zealand truffles is walking me through his farm, Limestone Hills, set along the edge of a jagged gorge above the Waipara River. He is talking to his seven-year-old beagle, whom he’s wryly nicknamed the Truffle Machine. Despite the sensory distractions of a ripe autumn afternoon, she has managed to deliver on the promise of her moniker.