Melt butter and chocolate chips in a large saucepan over low heat, about 4-5 minutes. Mix in the evaporated milk, whisking constantly. Slowly sift in the powdered sugar, continuing to whisk continuously to make sure there are no lumps. Bring to a boil for 4-5 minutes until thick and bubbly. Stir in vanilla and cinnamon for an extra special depth of flavor. Serve while warm over favorite desserts. Keeps in the refrigerator in a sealed container up to 6 weeks.
