Lemons from the Amalfi Coast, almond paste from Sicily and hazelnuts from Piedmont are just a few of the exceptional ingredients Guido Martinetti and Federico Grom use for their outstanding Grom gelati and sorbetti. The duo opened their first gelateria in their hometown of Turin in 2003 and now have a three-month-old New York City spot. They’re so fanatical about ingredients that they broke ground this spring on their own farm, Mura Mura, in Piedmont (