Milk candies slow-cooked to creamy perfection are a beloved Mexican confection. This traditional, family-friendly sweet is a rich, caramelized treat that melts in your mouth.
In a large heavy-bottomed saucepan, combine whole milk and granulated sugar. Place the pan over medium heat and stir constantly until sugar dissolves completely.
Add baking soda, stirring well to incorporate. Increase heat slightly until the mixture just begins to bubble, then immediately reduce heat to low to maintain a gentle simmer.
Continue simmering uncovered, stirring frequently and scraping the bottom and sides of the pan to prevent sticking and scorching, for 70–90 minutes. The mixture will gradually thicken and turn a light caramel color.
Once the volume has reduced by half and the mixture coats the back of a spoon, stir in unsalted butter and vanilla extract. Cook for an additional 10 minutes over very low heat, stirring until smooth and glossy.
Remove from heat. Let cool 10–15 minutes, then spoon into molds or onto parchment paper in small rounds. Allow to set completely at room temperature before serving or storing.