Onion Soup

1/4 cup butter
5 large onions
5 cups beef broth (4 small cans)
1/2 cup dried celery leaves or dried celery flakes
1 large potato (peeled & quartered)
1 cup white port or cream sherry
3/4 cup vinegar (or more)
4 tablespoons sugar
1 cup heavy whipping cream
1 tablespoon dried parsley flakes
salt & pepper

Melt butter in a large pot.
Add quartered onions, beef broth, celery leaves or flakes, quartered potato & bring to a boil.
Cover pot & simmer on medium-low heat for 30 minutes.
Puree little by little in a blender, emptying the purée from the blender into another large pot.
Continue to purée little by little, so that it won't splash out of the blender & placing the purée in the 2nd pot, until all of the purée is in the 2nd pot.
Mix in the wine, vinegar & sugar.
Bring to boil again & then simmer on medium-low heat for 5 minutes.
Stir in the cream, parsley, salt & pepper.
Heat on low flame another 5 minutes & be VERY, VERY CAREFUL NOT TO BOIL!