Combine Ingredients: In a large, heavy-bottomed pot, mix the milk, sugar, and baking soda. Cook over low heat, stirring constantly to prevent burning. Thicken: Continue to cook, stirring frequently, until the mixture becomes thick and caramel-colored, about 1-2 hours. Flavor: Stir in the vanilla extract. Cool: Let the dulce de leche cool, then transfer to a jar. It will thicken further as it cools. Pro Tips:

Stir continuously and keep the heat low to prevent the milk from burning and sticking to the bottom of the pan. A drop of vanilla extract added at the end of cooking enhances the flavor.