
In a large saucepan over low heat, melt together the chocolate, butter, and sugar, stirring constantly.
Stir in the milk and cook 2-3 minutes more, until heated through.
Remove from the heat and stir in the vanilla, cinnamon, and salt.
Pour into mason jars and store in the fridge up to 2 weeks.
To reheat: microwave sauce in a glass container for 2 minutes, stirring halfway through and spoon over ice cream, cake, or cookies.