Heat the butter in a saucepan and sauté the leek and scallion for 2 to 3 min over medium heat. Add the diced rutabaga or turnip and continue cooking for 3 min. Add the chicken broth and bring to a boil. As soon as it boils, reduce heat and simmer for about 30 min, until the vegetables are tender. Process in the blender until smooth. Return to the saucepan and add the maple syrup and the cream. Season to taste.