Combine chocolate, butter, and sugar together in a large saucepan over medium-low heat, stirring constantly.
Once the chocolate mixture is smooth, add the milk and continue stirring constantly for 2-3 more minutes.
Remove from heat and add in all remaining ingredients.
To store: Pour into glass jars and store in the fridge up to 2 weeks.To reheat: microwave sauce in a glass container for 2 minutes, stirring halfway through. Only microwave the portion you intend to eat, not the entire jar. Makes about four cups total.