The Old Elk’s Sour Mash Reserve is a throwback to the brand’s start-up roots, the distillers said. The founders a number of years back reached out to industry veteran Greg Metze, who is now their master distiller, to create a custom mash bill to craft a smooth, innovative whiskey.  The result? A unique, high-malted barley content bourbon of 51% corn, 34% malted barley and 15% rye.