Homemade Condensed Milk

In a medium saucepan, combine the milk and sugar.

Cook over medium heat, stirring frequently, until the sugar is dissolved and the mixture comes to a simmer.

Reduce heat to low and simmer, stirring occasionally, for about 30-40 minutes, or until the mixture thickens and reduces by about half.

Stir in the butter and vanilla extract until well combined.

Let the condensed milk cool completely before using or storing in an airtight container in the refrigerator for up to 1 week.