In a large saucepan, saute onion and carrot in butter until onion is tender. Add parsnips; cook 2 minutes longer.
Stir in the chicken broth and seasonings; bring to a boil. reduce heat, cover and simmer for 12 to 15 minutes or until parsnips are tender.
Carefully place the ingredients into blender container and blend until smooth. Return puree to pan. Add a tablespoon of the hot mixture to temper the milk, stir and slowly add milk to soup and heat through.