Yucca must be cooked before eating.  Yucca should be peeled before cooking.  Boil, steam, bake. or microwave the root until tender.  Boil chunks of the roots with water to cover for 15 to 20 minutes or until they are very tender.  Roots can be baked whole at 375 degrees F. for 40 to 60 minutes or until tender.  Microwave the roots, chopped, sliced, in 2 tablespoons water in a loosely covered in shallow dish.  Microwave on high for 5 to 8 minutes or until tender, then let stand for 2 to 3 minutes before service.