It stands to reason that Johnnie Walker’s master blender, Jim Beveridge—with more than 8 million barrels of whiskies aging in numerous warehouses throughout Scotland—would have quite a challenge if he wanted to select just three of these casks from which to make a superpremium, super-refined vatting. But with the John Walker & Sons Odyssey ($1,100) he has done precisely that. Inspired by Alexander Walker’s passion for epic journeys (plus his original blending notes), the Odyssey is the first triple-single-…