1.

Preheat oven to 425°F. Pour sweetened condensed milk into a small glass baking dish or pie plate and cover with aluminum foil. Place dish in a larger baking dish and pour in hot water until it reaches halfway up the side of the smaller dish. Transfer to oven and cook until condensed milk has become deep golden brown, about 1 hour. Remove from oven and whisk dulce de leche while still hot. Let cool slightly and then use while still warm or transfer to an airtight container and store in the refrigerator for up to a month.