Melt the chocolate in a saucepan on low heat. Once it's melted, add the sugar and slowly mix in the evaporated milk. Mix until combined and bring to a boil. Boil for 3-4 minutes until thickened. It will thicken more after it cools.
Recipe by HoneyBear Lane at http://www.honeybearlane.com/2013/02/hot-fudge-valentines.html