n n On medium heat, cook diced celery and onion in olive oil until tender. Remove from pan and set aside.n n Reduce heat to low, add butter and flour to pan, stirring constantly to combine. Cook until light tan in color.n n Add 1 cup milk, stirring to blend. Add the second cup of milk, continuing to stir over low heat until slightly thickened.n n Return vegetables to pan and add chicken broth. Simmer 10 minutes.n n Garnish with chopped parsley and serve.nn