Place beans in a large, heavy pot. Add water to cover beans by two inches, and let soak overnight. Drain beans.

Heat olive oil in a large, heavy pot over medium-high heat. Add onion, leek, tomato, carrots, celery and garlic, and sauté until vegetables are tender, about six minutes.

Add beans, chicken stock, thyme and rosemary. Bring to a boil, then reduce heat to medium-low. Cover and simmer until beans are very tender, stirring occasionally, about one hour.

Purée soup until smooth. Add whip topping and season with salt and pepper. Ladle soup into bowls. Lightly drizzle with truffle oil, if desired.