Melt the butter in a soup pot. Add onions and carrots and cook over low heat, covered, until vegetables are tender, about 25 minutes. Add parsley, stock and potatoes and bring to a boil. Reduce heat, cover, and simmer until potatoes are very tender, about 30 minutes. Add dill, remove soup from heat and let it stand, covered, for 5 minutes. Pour soup through strainer and add solids to food processor. Add 1 cup of cooking stock and process until smooth. Return pureed soup to cooking pot and add additional cooking liquid until soup reaches desired consistency. Add salt and pepper to taste and gradually stir in grated cheese. When all the cheese is incorporated and the soup is hot, serve immediately.