Chop one bunch of green onions. Heat 1 tablespoon of oil and 2 tablespoons of butter in a pan and saute the onions over a gentle heat for 3-4 minutes. Chop two small potatoes, add them to the onion (along with one chopped celery stalk if desired), and cook several minutes. Cut one pound (approximately one bag) of carrots into small chunks and add to the pan. Fry over low heat for 3-4 minutes, stirring frequently, and then cover. Reduce the heat even further and cook for about 10 minutes (shaking the pan occasionally to keep vegetables from sticking). Add 4 cups chicken or vegetable stock, bring to a boil and simmer until potatoes and carrots are tender (approx. 8-10 minutes). Add one cup of milk. Process soup in a blender. Fry 2-3 teaspoons ground coriander in a tablespoon of butter, remove from heat, add 1 tablespoon cilantro (or more if you like), salt and pepper to taste. Stir coriander/cilantro mix in soup and serve hot or cold (garnished with a few fresh cilantro or parsley leaves).