In a large saucepan, combine 1 c potatoes, chicken broth and onions. Bring to a boil. Reduce heat and cover. Simmer for 10 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 mintues or until vegetables are tender. Add tuna. Simmer 5 minutes more.