How to Make It
In a medium saucepan, cover the beans with 4 cups of water, add the garlic and bring to a boil. Reduce the heat, cover partially and simmer the beans until tender, about 45 minutes. Add 1 teaspoon of salt and let the beans cool in their liquid; discard the garlic.
Meanwhile, in a large saucepan, heat the olive oil. Add the onion and cook over moderate heat until translucent, about 8 minutes. Add the carrots, leek, fennel and celery and cook until softened, about 6 minutes. Add the chicken stock, tomatoes, thyme, bay leaf and 3 cups of water and bring to a boil. Reduce the heat, cover partially and simmer until vegetables are tender, 25 minutes.
In a small skillet, heat 1/4 cup of the olive oil. Add the pumpkin seeds and garlic and cook over moderately high heat until the seeds turn light brown, 2 to 3 minutes. Scrape the contents of the skillet into a food processor and let cool. Add the carrot tops, parsley, cheese and remaining 1/4 cup of olive oil and process until smooth. Season the pistou with salt and pepper.
Add the green beans and zucchini to the soup and simmer until crisp-tender. Stir in the ditalini and cooked beans with their liquid and bring to a simmer. Season with salt and pepper. Serve the soup with the pistou.