How to Make It
Mix milk and sugar in a large, heavy-bottom sauce pan.
NOTE: Make sure the pan is large enough for the sauce to froth up when the baking soda is added later.
Add the cinnamon stick, salt, and vanilla extract. Bring to a boil on a medium- high heat white constantly stirring. This will take about 15 minutes – you must watch carefully or it will boil over in a heartbeat!
Once the milk boils, remove from the heat and add baking soda to the pan. The mixture will froth, bubble, and grow- just keep stirring well.
Place the pot back over medium heat and stir often, at least every 10 minutes. Keep the milk at a gentle simmer (not a raging boil). Stir well, especially along the bottom of the pan so it doesn’t scorch. Adjust heat as needed.
After 1 to 1 ½ hours, the milk will start to turn golden brown. Remove the cinnamon stick.
The caramel will begin the thicken quickly. Keep stirring for 15- 30 minutes. The longer you cook it here, the harder and stiffer the sauce will be.
Once it is a rich brown and thick enough to coat the back of a spoon, remove from heat and allow to cool just a bit. Pour into an airtight container and refrigerate for up to a week.