Prepare the Jars

1. Wash and scald three 8-ounce canning jars.
2. Divide the sweetened condensed milk among the 3 jars. Add a pinch of salt to each jar, if desired. Or leave it in the unopened cans.
3. Place the lids on the jars and screw them on tightly.

Slow Cooker Preparation

1. Place the jars in the slow cooker and add water to a depth of 1 inch above the tops of the jars. If you leave the sweetened condensed milk in the cans, place a small towel in the bottom of the slow cooker. People have complained about stains from cans in the crockery inserts.
2. Cover the pot and cook on high for 2 hours. Reduce the heat to low and cook for about 4 to 5 hours longer. Lift a jar out of the water and take a look at the color. It should be a medium golden brown.

Storage

1. Store the finished dulce de leche in the refrigerator for up to 2 weeks (the jars will appear to be sealed, but they are not shelf stable). After opening, use the caramel within 5 days. If you cooked the caramel in the can, store it unopened at room temperature for up to 3 months.
2. Alternatively, pour the caramel into freezer containers and freeze for several months.
3. Heat the dulce de leche and thin with water or cream, if necessary. Drizzle over cake, desserts, and ice cream.