It's astonishing that such a luxuriously smooth, rich, sweet concoction as dulce de leche can be made from just one ingredient, condensed milk -- without even opening the can!
Place a can of sweetened condensed milk (with the label removed) on its side in the bottom of a stockpot filled with water. Gently boil 2 hours, replenishing the water as necessary to keep the pot full and the can submerged. (This prevents it from bursting.) Using tongs, transfer the can to a wire rack and let cool completely before opening. Drizzle the caramel over ice cream, or use it as a filling for sandwich cookies. (Leftover dulce de leche can be stored in the refrigerator in an airtight container and rewarmed in a double boiler or microwave.)