Cut the hearts of palm into 3/4inch rounds and quickly saute in butter. Add reserved liquid and chicken stock. Cook over medium heat stirring for 2 to 3 minutes. Transfer to a blender and puree. Strain through a sieve and return to a sauce pan. Temper 1 egg yolk with some of the hot liquid and whisk into the puree. Season with salt and pepper. Ladle into warm soup bowls. Combine the parsley and yogurt and place a dollop on top of the soup as a garnish.
c.1997, M.S. Milliken & S. Feniger, all rights reserved