If you must.....use less butter or use Smart Balance w/butter and fat-free sour cream.  But, everything in moderation.  It's a great party dish!!  YUMMY!
 <img src="http://www.traveltalkonline.com/forums/images/graemlins/handshake.gif" alt="" />  Contessa
BTW...Georgia, fresh tarragon would be great!! <img src="http://www.traveltalkonline.com/forums/images/graemlins/Clapping.gif" alt="" />