In a large saucepan, combine one cup potatoes, chicken broth, and onions. Bring to a boil. Reduce heat and cover. Simmer for ten minutes or until potatoes are tender. Add sage, paprika, and white pepper. Mash potatoes. Add remaining potatoes, carrots, green beans, celery, and milk to mashed potatoes. Bring just to a boil. Reduce heat and simmer for 15 minutes or until vegetables are tender. Add tuna and salt. Simmer five minutes more.