How to Make Crystal Clear Cocktail Ice at Home

Pour the filtered water into the insulated cooler.Leaving the cover open, freeze the cooler in your freezer for 24 hours. (Don’t leave it in the freezer for longer than this, because you don’t want the ice block to freeze all the the way through.)Remove the cooler from the freezer. Place a cutting board in your sink to catch the ice block, then turn the cooler upside-down over the sink to release ice.Under hot running water, use the knife to chip off the partially-frozen layer of ice, leaving only the clear layer of ice. Smooth out any jagged edges under the running water.Place the ice block on a cutting board. Score it about 1 – 2 centimeters deep with the serrated knife, then gently strike the knife with the mallet to break the ice off in a clean block. Use the same procedure to break that ice into your desired size and shape.Use the ice cubes immediately, or store them in a ziplock bag in the freezer. A layer of frost will form on the outside of the stored ice cubes, so when you’re ready to use them, let the ice cubes come to temperature on the countertop for a few moments so that the frost melts and they become clear again. (Don’t run them under warm water to remove the frost because at this point the ice will crack.)