Dulce de Leche

Directions

1. 1
   Place the vanilla bean, 3 cups of the milk, the sugar, water, and baking soda in the insert of the slow cooker, and whisk them together.
2. 2
   Cook for 9 hours on HIGH, uncovered, then remove the vanilla bean and whisk the milk mixture gently.
3. 3
   Use a dull-edged butter knife to carefully scrape down the crust of sugar that accumulates on the sides of the insert.
4. 4
   Do not skim the foam off the top of the mixture.
5. 5
   Continue cooking for 1 more hour, stirring every 20 minutes, until it is a rich medium-caramel color and has thickened to the consistency of melted ice cream.
6. 6
   In the meantime, warm the remaining 1 cup of milk in a small saucepan.
7. 7
   Turn off the slow cooker, and stir in the warm milk.
8. 8
   (This will prevent the dulce de leche from hardening while refrigerated.)
9. 9
   Carefully remove the insert.
10. 10
    Allow the mixture to cool for 10 minutes, then spoon and scrape it into a small metal bowl.
11. 11
    Cover and cool to room temperature.
12. 12
    The mixture will thicken slightly as it cools.
13. 13
    Refrigerate it in a tightly covered container for up to 3 months.