Caramelize the sweetened condensed milk: Immerse unopened can of Eagle Brand Sweetened Condensed Milk in a deep heavy pot (with a heavy lid that fits snuggly to avoid evaporation), with enough water to cover the top of the can by an inch. Bring water to boil, lower the heat and cover the pot. Continue to simmer 1 hour and 30 minutes after it begins to boil. Check the pot every 20 minutes or so, adding more boiling water if the water level becomes lower than the height of the can. Leave can in the pot of water until it cools. DO NOT open can until it has completely cooled, it will ooze out and make a mess. This can be done several days in advance.