How to Make It
Stir together first 6 ingredients in a large bowl. Pour mixture into a 13- x 9-inch pan; cover and freeze at least 2 hours.
Process half of mixture in a food processor or blender until smooth. Remove from processor, and set aside. Repeat procedure with remaining mixture. Return all of mixture to pan.
Cover and freeze at least 4 hours or until firm. Garnish, if desired.