Combine breadcrumbs, celery, onion, salt, pepper, sage, and 3 tablespoons melted butter; mix well, and set aside.
Place steak between two sheets of waxed paper. Flatten to 1/8-inch thickness, using a meat mallet or a rolling pin. Cut steak into 8 portions. Place 2 tablespoons stuffing down the center of each piece. Roll up jellyroll fashion, and tie securely with string.
Dredge each veal bird in 1/2 cup flour. Brown in remaining melted butter in a heavy skillet over medium heat. Add chicken broth; cover and simmer 30 minutes or until veal is tender. Transfer veal birds to a warm serving platter, reserving pan drippings.
Combine 1 teaspoon flour and sour cream, stirring until well blended. Add sour cream mixture to pan drippings. Cook over low heat 10 minutes or until thickened, stirring constantly. Spoon sauce over veal birds to serve.