Saute 1 sliced onion in a skillet with butter until golden. Add 1 chopped carrot, fresh oregano, salt and pepper; cook 2 minutes. Peel 1 bunch celery; cut into long pieces and add to the skillet with 1 cup chicken broth. Cover and simmer until just tender, 20 minutes; uncover and boil to thicken. Stir in more butter and chopped parsley.