Peel and finely slice pumpkin, carrots and potatoes. Chop peeled onion and saute in butter in a deep saucepan. Cover with broth and bring to a boil. Add potatoes, carrots and pumpkin and cook on low heat under the cover for about 45 minutes. Add salt and pepper. Transfer broth mixture into the container of a blender or processor. Process until smooth. Add milk, warm up, do not boil. Sprinkle with pumpkin seeds and serving.