...I always cringe whenever I see a recipe for that calls for heating the unopened can in hot water. That is very dangerous and highly discouraged by the manufacturing companies. A safe practically fool-proof method is to use a 1 quart crockpot.
Pour 2 14-ounce cans of sweetened condensed milk (or 2 14-ounce cans nonfat sweetened condensed milk) into a 1 - quart slow cooker
Cook, covered, 6 to 7 hours or until mixture reaches the caramel color
desired.