Adding semi-sweet chocolate chips give this sauce a thick but pourable consistency while also adding extra chocolate flavor.
In a small saucepan, combine all the ingredients. Cook over medium-high heat, stirring, until the chocolate is melted and combined with the milk. Remove from the heat. Cool sauce slightly before using.
Store in an airtight container in the refrigerator up to 2 weeks. Before serving, reheat in a saucepan or microwave, stirring occasionally.