Beat first 6 ingredients at low speed with an electric mixer 30 seconds or until blended. Beat at medium speed 2 minutes. Stir in chocolate chips. Pour into a lightly greased 4-quart round slow cooker.
Cover and cook on low setting 4 hours or until set around the edges but still soft in the center. Turn off slow cooker and let stand 20 to 30 minutes; do not lift lid until ready to serve. Serve with vanilla ice cream.