Melt butter in saucepan. Add the carrots, onion and potato; cook for 10 minutes. Stir occasionally. Add the bay leaf, chicken broth, curry powder, and marjoram. Bring to a boil; lower heat and simmer until all the vegetables are tender. Remove the bay leaf. Puree with a blender or food processor. Stir in cream; add salt and pepper to taste. Add extra chicken broth if soup is thick.