Classic version

Cup of Yum
1. In a large saucepan or pot over medium heat, stir together the milk, sugar, and baking soda.
2. Bring to a boil uncovered. Whisk occasionally so bottom of saucepan doesn't scorch. Remove the saucepan from the stove if it looks like the mixture is going to boil over. Keep whisking until the foam subsides and then return to the stovetop. Once mixture is boiling consistently without foaming, reduce heat to low and simmer, uncovered for 1 ½ hours, stirring occasionally, until the milk has caramelized and thickened. Cooking the milk and sugar low and slow until it caramelizes and thickens, resulting in a deep golden brown sauce. Be patient!
3. When the mixture has thickened to where it sticks to the back of a spoon, remove from heat and stir in the vanilla and cinnamon.
4. Carefully transfer to a glass jar to cool. Dulce de Leche will thicken as it cools.

Boiling Method (sweetened condensed milk)

1. Remove the label from sweetened condensed milk can. Place can(s) in a saucepan or pot large enough to accommodate them. Fill with water so the cans are submerged by 1-2 inches.
2. Bring to a boil over medium high heat. As soon as the water comes to a boil reduce to low and simmer for 2 hours for a light golden color and 3 hours for a dark amber color with a richer flavor. Add more water if needed to keep can(s) covered.
3. Allow to cool and whisk to smooth out any lumps.

Baking Method (sweetened condensed milk)

1. Preheat oven to 425°F. Pour sweetened condensed milk into a pie dish or cake pan and cover tightly with foil.
2. Transfer to a deep roasting pan and fill with hot water until 1-inch of depth. This is what's called a bain-marie.
3. Bake for 1 hour 45 minutes. You can add 15 more minutes time for a darker amber color and richer flavor.
4. Allow to cool and whisk to smooth out any lumps.