Prep and Cook Time: 35 minutes. Notes: Piñon nuts, grown in the Southwest's high desert, are the intensely flavored cousins of the more common Italian pine nut. Either variety works well here. You can make the sauce up to 1 week ahead; refrigerate in an airtight container, then gently rewarm over medium-low heat.
1. Pulse nuts in a food processor until coarsely ground (the texture of couscous).
2. 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.
3. 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.