Peel squash and cut into 1/2 inch cubes. Place in large saucepan. Add enough water to just cover. Simmer until squash is tender. Meanwhile, heat oil in skillet. Add onion and garlic. Sautee until onion is soft. Add carrots, cover and cook about ten minutes. When squash is tender, pour squash and liquid into food processor and blend until smooth. Return to saucepan and add sautéed vegetables. Dissolve miso in 1/2 cup warm water and blend into soup. Heat gently (about 20 minutes) until flavors blend. Add cilantro. Add cayenne to taste.