One 12-ounce bag semisweet chocolate chips or 12 ounces semisweet chocolate, cut into chunks
4 tablespoons unsalted butter
2 teaspoons instant espresso
1 teaspoon pure vanilla extract
In a medium saucepan, combine the condensed milk, chocolate, butter and espresso and cook over low heat, stirring, until the chocolate is completely melted and the sauce is smooth. Remove from the heat and stir in the vanilla. Transfer the sauce to a small pitcher. Serve over ice cream.