Stovetop method:
Take a can of sweetened condensed milk and remove the label.
Place the can in a large pot and fill the pot with water, making sure the water level is at least 1 inch above the can.
Reduce the heat to a low once the water has reached a boiling point.
Simmer the can for 2-3 hours, making sure the water stays at a low boil and that the can is always submerged.
After 2-3 hours, turn off the heat and carefully remove the can with tongs.
Before opening the can, let it cool all the way down.
Oven method:
Preheat your oven to 425°F (220°C).
Take a can of sweetened condensed milk and open the can.
Condensed milk should be poured into an oven-safe dish and covered with foil.
Place the dish in a larger baking dish and fill the larger dish with hot water, making sure the water level is about halfway up the side of the smaller dish.
Bake for 1.5-2 hours, or until the condensed milk is thick and caramel-colored.
Before using, remove it from the oven and allow it to cool.
Slow cooker method:
Take a can of sweetened condensed milk and remove the label.
Place the can in a slow cooker and fill the slow cooker with water, making sure the water level is at least 1 inch above the can.
Cook on low for 6-8 hours, or until the condensed milk is thick and caramel-colored.
Turn off the slow cooker and carefully remove the can with tongs.
Prior to opening the can, allow it to cool completely.
Note: It is very important to make sure the can is completely covered with water at all times during cooking to prevent it from exploding. The can shouldn't be opened while it's still hot.