In a large saucepan, saute carrots, celery, leeks and jalapeno in butter for 10 minutes. Add the squash, broth and ginger; bring to a boil. Reduce heat; cover and simmer until squash is tender, about 25 minutes.
Cool until lukewarm. In a blender or food processor, puree squash mixture in small batches until smooth; return to pan.
Add cream, salt and pepper; mix well. Heat through but do not boil. Garnish with pecans. Yield: 8 servings (2 quarts).