Pulse nuts in a food processor until coarsely ground (the texture of couscous).
Sift sugar, cocoa, and salt into a medium saucepan. Add 3/4 cup warm water and stir to combine. Bring mixture to a simmer over medium heat, stirring until smooth.
Add cream, corn syrup, vinegar, and chocolate chips. Raise heat to medium-high and boil mixture for 8 to 10 minutes, swirling occasionally, until slightly reduced (mixture will be thin and sticky); remove from heat. Stir in unsweetened chocolate, butter, vanilla, and pine nuts. Serve warm.
With a Measure of Grace: The Story and Recipes of a Small Town Restaurant; Hell's Backbone Grill