Step 1 Melt 5 1/2 tablespoons of butter in a medium soup pot. Add the carrots, celery and onion and saute over medium heat until they are transparent, 10 minutes.
Step 2 Add the stock and bring to a boil. Simmer until the carrots are tender, 20 minutes. Strain the vegetables and transfer them to a food processor. Puree and return to the saucepan.
Step 3Add the cream, orange juice and ginger. Simmer 10 minutes.
Step 4Melt the remaining tablespoon of butter in a small saucepan. Add the flour and cook, stirring, until smooth. Add this to the soup mixture and cook, continuing to stir, until the liquid thickens slightly, about 3 to 4 minutes.
Step 5Reduce the heat and add the sugar and salt and pepper to taste.