In a heavy medium saucepan, heat the milk and the dulce de leche, stirring until well blended. Add the chocolate and whisk until chocolate is melted and the mixture is smooth. Allow to cool.
In a medium bowl beat the heavy cream with an electric mixer until it forms soft peaks. Gently fold the heavy cream into the cooled chocolate mixture.
Divide into 6 decorative glasses and refrigerate until firm, about 4 hours.
PREPARATION FOR HOMEMADE DULCE DE LECHE
Stir together the milk, sugar, and baking soda in a heavy 3 to 4 quarts saucepan. Bring to a boil, then reduce the heat and simmer uncovered, stirring occasionally, until caramelized, golden color, and thickened, about 1 ½ to 2 hours. After about 1 hour stir more often as milk caramelizes and burns. Stir in 1 teaspoon vanilla.