Preheat oven to 425 degrees F.

Boil a full kettle of water.

Pour the condensed milk into a baking dish that is small enough to be placed in a larger baking dish. Place the smaller dish inside a larger baking dish and then fill with the boiling water until it's about halfway up the sides of the smaller baking dish.

Transfer dishes to the oven and bake for at least 1 hour and 45 minutes or until golden brown.

Enjoy right away (like on my 3-ingredient brownies) otherwise, transfer the dulce de leche to an airtight container for storage in the refrigerator!