Though most may believe that a potato is a potato is a potato, ???There???s a real difference in taste,??? says Daryl Mosher, who grows 10 varieties of potatoes on five acres at Brittany Hollow Farm, in Rhinebeck. ???People come up to our stand from Ireland or parts of Europe, and they say ???This is the first time in 20 years I???ve had a real potato.??? It???s nothing like your standard white su