In a large, heavy-bottomed pot, combine the whole milk, granulated sugar, and baking soda. Stir to dissolve the sugar.
Place the pot over medium heat and bring the mixture to a gentle boil, stirring constantly to prevent the milk from scorching.
Once the mixture comes to a boil, reduce the heat to low and simmer. Continue to cook, stirring frequently, until the mixture thickens and turns a deep caramel color. This process can take 1.5 to 2 hours.
To check if the dulce de leche is ready, drop a small spoonful onto a plate. It should hold its shape and be thick but spreadable. Remember that the mixture will thicken further as it cools.
Once the desired consistency is reached, remove the pot from the heat and stir in the vanilla extract.
Let the dulce de leche cool slightly before transferring it to a jar or airtight container.
Store in the refrigerator for up to two weeks.
Note: Dulce de leche is a rich and creamy caramel-like sauce that is popular in Uruguay and throughout Latin America. It can be used as a topping for desserts, spread on toast, or enjoyed by the spoonful.
Enjoy your meal!