- In large soup pot, heat 1 tablespoon oil over medium heat.
- Add potatoes, carrots and celery and cook, stirring, about 5 minutes.
- Add 8 cups water, bouquet garni and saffron if using.
- Bring to a boil, reduce heat and simmer 10 minutes.
- Add green beans and continue to cook until vegetables are almost tender, about 25 minutes.
- Add zucchini and macaroni and simmer until pasta is tender, an additional 10 minutes.
- Season with salt and pepper to taste, stir in parsley and drizzle with remaining ½ tablespoon oil.
- Remove from heat, cover and keep warm.
- In small skillet, toast hazelnuts over medium-high heat, stirring often, 5 minutes.
- While nuts are still warm, place in folded tea towel and rub vigorously to remove skins.
- Transfer nuts to food processor, add garlic and process until finely chopped.
- Add basil or parsley and tomato and process, scraping down work bowl as necessary, until mixture forms a smooth paste (add water to thin as necessary)
- Transfer to small bowl, add salt and pepper and stir in ½ tablespoon oil.
- Ladle soup into shallow soup bowls or transfer to serving dish.
- Stir in pistou or pass separately for guests to stir in desired amount themselves.