Dulce de Leche

Bring milk to a boil in a large saucepan over medium-high heat. Remove from heat; strain through cheesecloth. Return to pan.

Cut vanilla bean in half; scrape seeds into milk. Stir in sugar; heat over medium-high heat, stirring constantly, until sugar is dissolved. Stir in baking soda just as milk mixture begins to boil. Reduce heat to medium, stirring constantly, until mixture thickens, a wooden spoon drawn through mixture leaves the bottom of the pan visible, and mixture is light brown. Remove pan from heat.

Fill a large bowl with ice and cold water; place pan into ice bath, stirring constantly until dulce de leche is cold. Transfer to sterile airtight jars; store in the refrigerator.