Here's another from Yankee's former “Recipe with a History” column. Dorene Lengyel of Lynnfield, Massachusetts. For Dorene's mother, this sauce was her vacation from cooking. It's easy and delicious.
In a small bowl, whisk together sugar, cornstarch, and salt. Set aside.
In a 2- to 3-quart saucepan, melt chocolate with milk and butter over medium-low heat. Simmer 3 minutes, then whisk in dry ingredients and cook, stirring, for 5 minutes. Mixture will thicken and become smooth and glossy. Turn off heat and add vanilla. Serve warm.