In a mixing bowl, combine the first six ingredients. Beat on medium speed for 2 minutes. Stir in chocolate chips. Pour into a 5-quart slow cooker that has been coated with nonstick cooking spray. Cover and cook on Low for 6-7 hours or until a toothpick inserted near the center comes out with moist crumbs.
Serve in bowls with whipped cream or ice cream, if desired.