How To make Mushroom Soup Concentrate

2 pounds fresh mushrooms
1/4 cup minced fresh onion
1/2 cup celery

finely slivered
6 tablespoons butter
2 1/2 tablespoons minced fresh parsley
1 teaspoon salt
1/2 teaspoon paprika
4 tablespoons flour
2 cups broth :

beef, chicken or veg
Slice mushroom caps and chop stems. Set aside while you saute onion and celery in butter in a large heavy skillet or dutch oven 3 minutes. Add parsley and saute 3 minutes stirring with a wooden spoon. Add mushrooms. Sprinkle on salt, paprika and flour. Stir constantly until well blended. Add broth slowly. Bring to a boil. Lower heat and simmer 10 min.