3 300-millilitre cans of condensed milk
Transfer the condensed milk to four 250-mililitre Mason jars. Add lids and rings and place in a large slow cooker. Add enough water to cover the jars by 2 inches. Cook on low heat for 7 to 8 hours, carefully removing the jars at the end of the cooking period. Refrigerate until cool. Dulce de leche will keep for about a month in the refrigerator.
Sandwich it between sugar cookies for a take on alfajores or slather it on shortbread and top with chocolate for a shortcut version of Millionaire’s shortbread.