Why is it that ice cubes at home melt faster and turn your drink into a watery mass, yet your bartender’s ice stays chunky and cold until the glass is empty? Martin Wolf, a bartender at Berlin’s historic Frederick’s bar and restaurant, spills the secret with three cool serving hacks. Double freezing: “To make ice last longer, double freezing helps,” is Wolf’s top tip. Fill water into a cube maker and freeze. When the cubes are well frozen, pour them onto a plate or into a freezer bag and freeze them again. Go big: People tend to think that putting a lot of ice in the glass will water down the …